How do I get the apps menu button to work again?

[AC Question]

When I hit the white button with the six dots in the bottom middle it used to open so that I can see all of the apps, but now does nothing. Acts like it is going to open, but shows a blank screen with just my background picture. Had it happen before and took shut the phone off, took out the battery and both sd and sim cards and it fixed it. Tried that twice and nothing.