Why can't I see the phone app when on a call?

[EMD_CT]

When I make or receive a call, if I take the phone away from my ear, I cannot access phone app to place call on speaker, access keypad, or end call. This has happened since the latest Android up update. Using Nexus 5.

 

[B. Diddy]

Welcome to Android Central! Does the screen remain completely blank when you take it away from your ear?