Okay, I assume you turned it off and then turned it back on. So, my next thought would be maybe it is your system’s battery management that is somehow killing it. In which case, open thunder, then open the app’s witcher and then tap the thunder icon. Then tap app info and in the system settings there should be something for battery management. It will say that it is optimized for battery usage and you want to make it not optimized.
Okay, that’s weird. I honestly have no idea what’s causing that then. I’m sorry I couldn’t help more.