Exported MP4 file has no thumbnail and crashes constantly

[#1]

So the last week I've been having some weird issues with Adobe Premiere. After exporting the same I always do, Customer, H264 MP4 CBR 5.0, when the file is done, it no longer shows a thumbnail icon. It does for all the previous MP4 videos, so it looks like it is just music. When I go to play the video, it plays in Windows Media Player. When I try to upload to YouTube as soon as I click on the file to upload, my computer hangs and I have to shut Chrome down (latest version). When I try it on Microsoft Edge (the latest version) it does the same thing.

I don't know what is going on but it's frustrating I can't upload to Youtube unless I drag and drop the file. When I do it uploads and plays fine.

[#2]

I cannot edit/delete this post so I have to make a new post.