mp4 not showing in Windows Media

Greetings, I am exporting my project to .mp4 files using H.264 with Match Source - High bitrate.

When I used this exact setting last week, it worked just fine.
As of now, the video saves as .mp4 but there is no visual or audio in the playback in Windows Media.

When I click on the videos I created last week, they open and play just fine.

I am unsure of what to do as it seems like a "now you see it/ now you don't" type of issue.

When I look for info online, all the posts are from 2018 or older. 
Anybody have any ideas?