Imported clips are black. When dragged into composition, completely disappears.

[Bella30090655qdsd]

I recently bought After Effects so I am not super familiar with the program, so this could be a stupid mistake, idk. All clips that I import are completely black. I have tried to reinstall the program, however, this has not worked. Audio clips that I have imported also do not play at all. This all started happening after my After Effects crashed earlier today. 
I have AE 2023 and am on Windows 11 64-bit. Any help or suggestions would be great! Thank you!

[Andrew Yoole]

What is the source of the clip?  

If you create other components in your timeline like a solid or text layer, are these visible?

[Rick Gerard]

AVC MPEG video can be difficult to decode. Try transcoding the clips to a production format like ProRez HQ using the MOV presets in the Adobe Media Encoder.