and welcome to HF Empire forums!
Yes indeed, HFX is facing quite a few problems and they are not likely to get fixed by the author. It doesn't work on Android versions equal and above 8, and may not work on some Android 7's (this may be the reason it has been removed from Google Play Store, I'll see if I can fix it in the future but I don't know). The server is also not working so you cannot refer friends nor buy gems. It still works on iOS, and for Android you can get the apk on Google. If you'd like to chat, please join our Discord: https://discord.gg/3PUwmY8