Storyline3 Error: Uploaded mp4 format video to trim and save but receiving error "Video cannot be encoded"

Hi Jason, thank you for your question!

Sometimes re-saving the mp4, and then uploading it again to your Storyline project, will solve the issue. Here's a quick peek on how to do that! 

If that doesn't work, would you upload the file here so I can check how it's behaving? Or if you prefer, you can submit it privately to us here.