So I'm having the same issue.
C2 - R201
Using the video plugin and a webm and mp4 encoding for all videos (both of which play in VLC)
Basic actions to play from source (Note: my project works perfectly fine being run in Firefox, however, both Chrome and the APK generated by Intel XDK fail to play the exported video files)
Intel XDK (latest release as of 4/10)
Export through C2 using Cordova, for Android 4.0+
With all the above, I have exported my project and nothing is shown on my Android device.
I presume this is the same issue that causes Chrome to not play anything in the project.
Does anyone have any fix for this? It seems to be an awfully common error with little discussion.
Could this perhaps be an issue with permissions? Using the newest version of XDK, I have not added any other permissions because I presumed that, because nothing was noted in the manual, I would not need to check anything additional.