Articulate Rise - Videos and Mobile devices

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Anyone using Articulate Rise run across an issue with video playback on mobile devices? The videos work fine when accessing the LearnCenter on a desktop or laptop, but mobile browsers generate the error message below.

"The media could not be loaded, either because the server or network failed or because the format is not supported."

I found a few recommendations online - shortening the clip title to less than 15 characters and using Handbrake to convert the mp4 file to web-optimized - but nothing seems to work.