MP4 support in Adobe Express

Hey @1530387_Sołtan9034, Welcome to our Adobe Express community! 

This shouldn't be happening. Can you please specify the workflow where you're trying to upload an MP4 file, and it's not working? Please share a screen recording so we can understand better.

We'd like to know if you're uploading an MP4 file to start a project with or if you're trying to upload within any Adobe Express project. What platform or browser are you using? Is it happening with other file types, like PNG, JPG, etc. 

Also, try clearing out the cache/cookies of the browser or working on private/incognito mode to see if that makes any difference. 

Thanks!

Amitej