S9+ screen off when I pull it away from my ear

[basheirt]

I know there's a setting somewhere, but when I move the phone away from my ear, my phone screen stays off. It used to (until very recently) turn on when I pulled it away. Any idea what might have happened?

Now, when I say goodbye and move the phone to press the hangup button, I have to first turn the screen on with the power button.

Same if I have to press a number on a robo menu, want to go to speakerphone, open my calendar, etc. Not sure why the screen is staying off.

 

[Rukbat]

If you haven't changed anything, the proximity detector probably went bad.

But a case, or even a screen protector, could cause that if you recently added one. (The detector works by reflected light - phone to your ear, back to the phone.)