Can't import MP4 into Animate after compressing to H.264, Please help!

Hello! 

I am working on a 30 second HTML5 file video for an assignment on the 2023 version of Adobe Animate. I am trying to import a MP4 file to use in said assignment. I have all of my other content for the video imported into my library but when I try to import the MP4 into it, the option to "Import Video..." is greyed out as well as the videos in the file folder if I click the "Import to Library" button. 

I have re-ran this MP4 video through media encoder sevral times just to ensure I have the proper file format (H.264 per dr. Google's claims,) but to no avail.  I am running these programs on a Mac.

I would appreciate any insight that can be provided! Thanks!