Might this help ? https://addons.mozilla.org/nl/android/addon/external-video-player/ You can install vlc for instance to playback the video.

Thanks for the advice but every video in Firefox shows a box saying your device is not html 5 compatible!!! Yet if I click the YouTube link and go to YouTube it does the same , but click the main YouTube icon then click back in Firefox the video will play ??

Thanks for the advice but every video in Firefox shows a box saying your device is not html 5 compatible!!! Yet if I click the YouTube link and go to YouTube it does the same , but click the main YouTube icon then click back in Firefox the video will play ??

What happens when you tick the firefox main menu option 'request desktop website'?