Issue Summary

Media Viewer is not rendering or previewing MP4 videos. 

Steps to Reproduce

1. Create Confluence Page
2. Add Video Attachment (MP4) to the page
3. Publish Page
4. Click on ... > Attachment > Files
5. Click on View for the attachment

Expected Results

Media Viewer should render/preview the video

Actual Results

We have seen 2 different behaviors:

• The Media Viewer presents the message: We can't preview this file.
  You'll have to download the file to view it.
• The Media Viewer attempts to load the video without timing out

Workaround

Currently, we have the below paths:

• Right click on view and open in another table
• Click Directly on the files name

Both of these allow the browser to show the video install of media viewer