Light and proximity sensor stopped working

I have an iPhone 8 Plus, bought it last December. During the last few days, I think ever since I upgraded to the latest iOS version, the light and proximity sensor doesn't work - the light doesn't dim according to the room and when on call the screen remains active, causing me to accidentally click buttons.

The phone hasn't had the screen changed (which I read online might be a reason for these problems, but isn't the case here).

What else could cause this? And how do I solve it? Already tried restarting the phone and playing with the accessibility settings.

Thanks!