I've recently switched my employers self-hosted video player from Flash to HTML5 Video. Since the switch, we have had increasing numbers of users report that they are unable to play our videos.
Through a series of error-reporting functions, and further tests with users I can say conclusively that the issue is with the video files themselves. The users are capable of playing the file type, and having compared with the likes of YouTube, Vimeo etc, I cannot see any clear reason why the way our videos are enconded would cause a failure. The issue largely affects users on older of lower-end devices, but not exclusively.
I have included screen grabs of a typical videos settings for review in case anyone is able to spot an obvious problem.
Image 1: https://i.stack.imgur.com/A3zOS.png
Image 2: https://i.stack.imgur.com/Hdu6I.png
Edit: The users cannot initiate playback at all. We have provided them with direct links to the video files, so their browsers can play them in their natural optimised state - and still nothing works.
The error reporting we have implement shows us a range of data from connection speed, device info, browser info, location and tracking various possible points of error throughout our full player. There doesn't appear to be any notable correlation between users other than almost all Chromebook users have issues. But many others do also.