App Preview Silently Rejected

When I try to upload an Apple App Preview to iTunesConnect, nothing happens. I get no error message whether I try to drag the video into the proper slot or if I try to open it.

Is there some way to identify what the issue might be?

It's an iPad preview in mp4 format and 1920 x 1080 resolution, 1200 x 1600, 30fps, and only 27 seconds long. The recording was made directly from the device using ScreenFlow.
App Preview Silently Rejected
 
 
Q