TV Picture Turned Black But There's Still Sound

My husband and I were watching Disney+ and when we pushed the button on the U Verse Remote to play the next episode, the TV picture went black but there's still sound.

 

My husband has tried:

1. Changing TV Channels (which we can hear the different channels but still can't see a picture)

2. Resetting the receiver by holding the power button for 10 seconds

3. Unplugging the receiver and waiting a full minute before plugging it back in

4. Changing the Input

5. Unplugging the HDMI cord and plugging it back in

6. Resetting the router

 

We can see the app tiles. Then when we're in an app (Netflix, Disney+, etc), we can see the tiles for the shows/movies. But when we click a tile, the screen goes black again but there's still sound. 

 

We're at a loss and don't know what else to do. Any assistance would be greatly appreciated!