The problems you are seeing are likely due to a major bug in iOS 17.4 that makes air pressure data unavailable to all apps that use it. Flyskyhy is affected by this, because it uses the air pressure data for the Lift and Altitude instruments, for the vario tone, and the altitude written in the flight log.
This means that the Altitude indicator and Lift indicator are not working anymore under iOS 17.4 (they show 0).

Upgrade to the latest version of Flyskyhy (at least 8.1.3) and follow the instructions in the popups to enable access to the pressure sensor again. To upgrade the app, open the Apple App Store app and tap on your initials in the top right corner. Then tap on “Update All”, or scroll down and tap on “Update” next to Flyskyhy.

DHV has changed the software on their servers in April 2022. You can still upload in the same way as before, but you need a new password specifically for the upload functionality. See the DHV website for details, under “Automatischer Upload” [in the German FAQ only].

You can find the extensions under the "Settings" tab: the right-most tab. The first three entries there give access to the extensions. When clicked, a screen with description of the extension opens up, with in the top-right a button with the price on it. Click that button to start the purchasing process.
Note that after purchasing the Airspaces extension, it can take a couple of minutes until they are downloaded and appear on the map; possibly longer with a slow internet connection.

The most likely cause that the extensions are blocked, is because you have disabled in-app purchases on your phone. For older iOS versions, you can enable them again in the Apple Settings app, under General→Restrictions. You only need to enable them temporarily during the purchase. For newer iOS versions, see Apple's instructions for how to enable in-app purchases.

You can place the new instruments from the XC extension anywhere you like on your screen pages yourself. A description for how to edit the screens you can find here. When enabled in the settings, the app will switch to the page with the thermal centring tool automatically when entering a thermal.

The portrait and landscape layouts are independent of each other. By default, there are two pages in portrait mode, but only one in landscape. You can easily change the complete layout of the screen, including adding pages, by pressing and holding anywhere on the screen. See the instruments description for details.

Flyskyhy has a variety of different vario tones to choose from. You can select your preference in Settings→Vario. These work well with external Bluetooth varios. Without such a vario, the lift values are calculated from the accelerometer and pressure sensor data of the iPhone itself. They still work well, but can occasionally be erratic, see below.
It is not recommended to use the Flyskyhy vario tones with an iPhone 5 or older, because the old iPhone models do not contain a pressure sensor.

Yes it does. First of all, it enables a more stable altitude display. The pressure information is synced with the GPS altitude before flight, to get a baseline. Then during flight, the altitude is only derived from the pressure sensor, as required by many competitions. See more details here.

The vario is also derived from the pressure information, but that was more difficult. The pressure sensor in the iPhone is extremely slow: it reports only one sample every 1.3 seconds, and it lags about 3 seconds behind the actually movement of the phone. As a consequence, I had to base the vario support in Flyskyhy mostly on the accelerometer data, using the pressure only as a reference. The result is a decent vario, although a Bluetooth vario is more reliable.

Starting with iOS 17.4, you need to enable Fitness Tracking and authorise Flyskyhy to access Motion & Fitness to use the pressure data in Flyskhy. Install the latest version of Flyskyhy, and follow the instructions that pop up when you first open the app on iOS 17.4 or newer.

Flyskyhy supports a wide range of Bluetooth varios. If the vario device can share data with an iPhone over Bluetooth Low Energy, then it will very likely work with Flyskyhy. Check with the device manufacturor to be sure.
You can select whether Flyskyhy or the bluetooth device should generate the vario tones (or both, if you like). Flyskyhy has a selection of different tones to choose from, besides the standard tone. You can also choose whether to use the GPS data from the vario (if supported), or from the iPhone. See more details here.

So far, only an iPhone version is available. Porting the app to Android would be a major undertaking both in time and costs. This is both because of the differences in operating system between iOS and Android, and because of the larger variety in hardware models running Android. Therefore, I have no plans right now to release Flyskyhy on Android.
If you find an app called Flyskyhy on an Android app store, then it is a scam.

The app is developed for iPhone, and does not have iPad-native support yet. That means it will likely run on iPad, but in "iPhone compatibility" mode, just like any other iPhone app. The iPad will simulate an iPhone and show its screen shown at a large scale. In order for Flyskyhy to work, the iPad needs to have GPS capabilities, therefore it needs to be a Cellular model. No guarantees can be given that it will work.
There are plans to develop an iPad-native version of Flyskyhy, but no promises can be give for when that will be.

You can add waypoints manually, both on the waypoints map screen, and on the waypoints editing screen. But Flyskyhy also supports loading waypoint files in various formats. If the waypoints file is available on a web site, simply open the link in Safari on the iPhone, and it will ask whether you want to open the file in Flyskyhy.
If you have the waypoints file on your computer, you can e-mail it to yourself, and then open the attachment in the email app on the iPhone.
Or you can use iTunes to transfer the file to Flyskyhy. Drag the file to the screen in iTunes where the Flyskyhy flight log files are visible. Make sure Flyskyhy is already running when you do that. 

Before your flight, press the Start button. This indicates to the app your desire to start a flight, and will put the app into Flight Mode. The app will check a number of things, will fix the screen orientation into place, enable vario tones, and ensure continued operation in the background even if you switch off the screen or close the app. It does not start the log.
The log does not record the period before you take off. It starts when you move faster than 3 m/s (10 km/h, 6.2 mph) for more than approximately 10 seconds, and will include the 20 seconds before that as well.
During flight the Start/Stop button will show the flight duration in hours:minutes.

To stop recording a flight, press the Stop button. If you accidentally press the Stop button while you are still moving, you will get a warning. 
If you have enabled automatic flight end, then the log is automatically stopped after your landing.

In order for Flyskyhy to function normally, and flights to be logged, it needs to have access to location information. That sounds easy enough, but a number of settings in the Settings app need to be set correctly for that:

• Location Services needs to be enabled, both in general and specifically for Flyskyhy. They can be switched on under Privacy→Location Services.
  
• Background refresh must be enabled, both in general and for Flyskyhy. You can find that under General→Background App Refresh.
  
• Airplane Mode must be switched off, otherwise the GPS does not work either. You can switch Airplane Mode on/off on the control panel that appears when you swipe upwards from the bottom of the screen. 
  
• Make sure that you press the Start button before your flight.

Note also that a flight log does not start until you take off. A take-off is determined when you fly faster than 10km/h (6.2 mph) for at least 10 seconds. In very specific circumstances, like cliff soaring in strong winds, your ground speed may stay below that limit, and a log will not be started.

You do not have to buy them again, simply tap on 'Restore Extensions' under the Settings. Make sure you are logged in with the same Apple ID as you used to purchase the app.

The app will work fine as a flight instrument without internet connection. All instruments should still work the same, and the flight is properly logged.
Maps that are already cached on the phone will be shown, but new maps will not be loaded. Before your flight, while on a good internet connection, make sure you preload the maps required for the area you are flying in.
Live tracking services will not work without internet connection.

When configuring a new phone, Apple gives the opportunity to install the new phone from a backup of the old Phone. If you choose that option, then all Flyskyhy data, including all flight logs, will be transfered to the new Phone. You only may need to setup new Fly pages, if the resolution of your new screen differs from the old one.

If you don't want to use that option, then you can upload the flight logs to your new phone from the backup of them on your computer. It is recommended to keep a backup of your flight logs on your computer anyways, because otherwise they will be lost if you loose or damage your phone.

A third possibility is to transfer the flight logs through iCloud. Open the Apple Files app on your old phone, select "On My Phone", and then Flyskyhy. Now tap the menu icon in the top right, and choose "Select". Then "Select All" in the top left corner. Then press long on one of the flight logs, and select the "Copy" option that comes up.
The next step is to navigate to "iCloud Drive". Create a folder there to hold your flight logs, and open that folder. Press long on the middle of the screen, and select "Paste". Your flight logs will now be transfered to Apple iCloud
On your new phone, use the reverse process to transfer your flight logs from iCloud to "On My Phone" > "Flyskyhy".

You can transfer flight logs to your computer through iTunes.

1. connect your phone with your computer and start iTunes
2. select the phone icon in the top left
3. select the File Sharing menu entry on the left (or the Apps entry in older iTunes versions)
4. you will see Flyskyhy in the list of Apps under File Sharing. Select it. You may need to scroll down.
5. now you can drag any .igc file from the list on the right to a folder window.
6. you can also drag any .igc file from your computer into the list, and it will automatically be added to the logbook in Flyskyhy.

How to backup to Windows computers
Of course, you can also email individual files to yourself directly from the app to transfer them.

The latest MacOS operation system (Catalina) does not have iTunes anymore. In that case, you can backup your logs through the Finder:

1. connect your phone with your computer through a USB cable and open Finder.
2. under Locations on the left, select your phone.
3. select the tab Files at the top.
4. now click the little triangle next to Flyskyhy to show the logs. It can take a while for them to appear if you have a lot of flight logs.
5. drag and drop, or copy/paste any logs to and from other Finder windows.

How to backup to MacOS computers
You can also use the Files app on the phone itself to transfer Flyskyhy logs.

The landing and launch sites in Flyskyhy come from paraglidingearth.com. If you add the site there, then Flyskyhy will eventually pick it up. Because this is partly a manual process, it can take up to a couple of weeks before it is visible in the app. If you want to speed up the process, then let me know on the support page after you have added the sites.

When upload of your flight log to a Leonardo server fails because of an “Incorrect user name or password” or “Invalid User account” error, then first re-check whether your username and password are actually filled in correctly. If so, then the problem could be due to confusion over the use of http: or https: for the server. Flyskyhy will always try to use https:, but some Leonardo servers return a user account error message for that. In that case, use the following method to explicity specify http: for the server:

1. Instead of “Upload to «your server name»” use “Other Leonardo server”.
2. Make sure that you choose the same server name as you had already.
3. Fill in the submit URL of the server, including an explicit “http://” at the start. The submit URL is usually the internet address of the server, followed by “/flight_submit.php”, but check with the server administrators if it doesn't work. For example, use the following URL for the XC Australia Leonardo server: “http://xcaustralia.org/flight_submit.php”.

Once you have uploaded at least one flight successfully, the “Upload to «your server name»” in the default list should be replaced with the new URL, and you can use it as normal again.

This is likely due to a side-effect of the hands-free function. The hands-free function makes it really easy to switch pages during flight: simply hold your (gloved) hand shortly over the top of the phone. However, there are a number of restrictions due to the way Apple has built this. If you hold your hand there too long, then the screen goes black, and it does not work at all in landscape mode. Also, when you use a phone holder that covers the top of the phone, then that will also trigger the function, and the screen keeps changing or goes black.
Note that Apple has used a different proximity sensor in iPhone 15 and newer models. For those models, you need to keep your hand on the top of the phone for a second or so, for it to work properly.
You can switch the function on/off in Settings→Other→Touch-free control. 

Stability of the app is a high priority goal. You should be able to rely on the app to keep functioning correctly in all circumstances. Unfortunately, it can occasionally happen that the app crashes. In that case, it is highly appreciated if you send the crash log to us, so that we have a chance of locating the fault and fixing it. You can locate crash logs as follows:

• In the Settings app of your device, navigate to Privacy & Security → Analytics & Improvements → Analytics Data.
• Scroll through this list to find the events whose names start with Flyskyhy. The list is alphabetical.
• Tap the Flyskyhy event that has the date and time of your crash.
• Tap the share icon at the top right.
• Email it to support@flyskyhy.com, add as much information about the circumstances as you can.

If there is no crash log for the date and time of the crash, then the app most likely ran out of memory. Make sure enough free memory is available on the phone before your flight.

Please let me know what feature you would like on the support page, and I will consider adding it.