Linux packaged project fails to load Media Player

I have a project where i use the Media player to play videos in game. When opening the packaged Linux build, the media fails to load.
I am using WebM and the WebM Media decoder. All works fine in Engine. I also make sure that the media files are in my movies folder, and are imported from here to the project.

I have done the same process for my Windows machine (using H.264 mp40 and changing the decoder to windowsMediaFoundation) and that works fine.

Any idea why this would be different for Linux?