No the resolution is not the problem. My screen size is 1280x720 and i just tested it with a 1920x1080 video, and it still displays it correctly.
Did you download the video from my page and tested it with it ?
Or you can try it with the video i used to show off the plugin:
https://pixabay.com/videos/nebula-space-universe-galaxy-stars-216463/
you can also pick different resolutions there.
does your videos have sound? because that could cause some issues (when playing in browser for example.)
One last thing! i was testing this plugin on my other pc which i havent touched in a while. And the videos also did not work.
But this was because the pc had some old drivers installed. (GPU etc.) Check if your computer is up to date and Update your drivers. (And Browser)