Hi,

I'm currently unable to unlock my phone. It won't allow me to use the fingerprint sensor, and when I put in my PIN, the screen just goes black for a few seconds, and then returns to the lock screen. I've tried restarting the phone and turning it off, but it won't allow this either. If I hold down the power button, the screen will go black after a few seconds, but if I click the power button again, the lock screen comes on. 

I have no idea what could have caused this. It was working perfectly fine earlier, and after about an hour and a half of being idle, when I tried to unlock it, this happened. I've experienced this once before with this phone a few years ago. I think it just sort of fixed itself.

Does anyone know what the problem is and how I can fix it? It's extremely frustration and strange.

Thank you in advance for any replies.