Nor playing in FireFox

Please note: this plugin is no longer in active development. It should still be functioning properly, but I will no longer be making updates to it.

I’m not able to get your example site to load at the moment, but it sounds like there’s either a problem with the OGV video source, which Firefox uses, or the server is not serving up the “video/ogg” mime type. Instructions for enabling that mime type can be found here: https://www.paulund.co.uk/change-wordpress-upload-mime-types. If that doesn’t fix it, try re-encoding the OGV video for Firefox.