This is a known issue in Google Play. Give it up to 24 hours to process your payment and update the data on your device( s). You can also try to open a web browser on your PC or mobile device, go to Google Play, find StbEmu Pro (direct link) and install it remotely onto your device(s).
This is a known issue on some devices made by Sony, Phillips and Xiaomi. Some other device may also have this issue.
To fix this issue you can make the app use system (global) volume level: in Settings > Common settings > check Always use system volume level. You need to reload you currently active portal from the app's menu for the changes to take effect.
Portals are located on your IPTV provider's servers, so unless your IPTV provider has an option to change UI elements, you cannot change anything there. Most portals don't support UI customization so the UI can only be changed by IPTV provider only.
When I add some channels to Favorites and reload portal they disappear. I cannot move favorite channels in the list
All channel lists, including favorites, are stored on your IPTV provider's servers. If the app doesn't load favorites or load them in a wrong order this means your IPTV provider has not configured the portal properly. This issue can only be fixed by your IPTV provider.
In most cases when buffering happens this means either your network connection or your IPTV provider's network connection is not good enough to stream video to your device. If you are sure your network connection is good try telling your IPTV provider about this issue.
StbEmu does not support m3u or any other playlists, only portals designed for MAG boxes.
Currently, this feature only works properly on Android 10 and older versions. Since Android 11 applications can only read and write files in their own folders. An app can request a permission to read or write files in other folders, however this feature doesn't work on some Android TV devices and some Set-Top-Boxes (STBs) and it won't be fixed 1, 2.
If you're using one of the devices where this feature does not work, unfortunately you won't be able to create or restore backups on such devices.