If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (e.g. Adblock Plus, NoScript, Flash Block, Ghostery) then make sure such extensions do not block content. There is security software that can interfere with loading content, so check that as well.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

See also:

• https://support.mozilla.org/kb/fix-video-audio-problems-firefox-windows

I haven't changed any security settings. I do have Adblock, but that was installed quite a while ago and I haven't had any problems with Vimeo until I installed 47.0.

firefox 50 in safe mode (and regular mode) for vimeo only (it appears)

I have this problem also. I click on play and the image goes blank and the counter goes to zero and stops, I can move forward and the image displays for that time but does not continue, this problem started with 50 beta and coninued thru to 50 final

greybert said

and continued thru to 50 final

There is no Firefox 50 Release yet (out Nov 15) as any site that claims this is misleading by posting a Beta build or the Release Candidate build1 as a Release.

Are you able to view HTML5 videos as a way to see what your system supports is to look at https://www.youtube.com/html5/

If you do not have blue checks for all then you may have a Windows K or KN. https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows

sorry I took it as final when the latest beta update was to ff 50.0

I have tick marks for all players except MSE & WebM VP9 and I've forced websites with flash to default to html5

note I read the "if you can't see videos" in the forum and I d/l and tried to install the media pack for windows k/kn and It said my version of windows does not support it

note vimeo has worked fine in the past the vimeo player seems to work except it wont actually play the video