see the answer: https://support.mozilla.org/en-US/questions/1006810#answer-595027

michaelcg said

Something to do with Brightcove?

Assuming you use Brightcove : that bug is supposed to be fixed :

https://bugzilla.mozilla.org/show_bug.cgi?id=1194662

Brightcove says :

"An unanticipated problem was encountered, check back soon and try again."

See : https://support.brightcove.com/brightcove-player-error-reference

^: that bug is about Firefox on mobile.

• Bug 1194662 - Videos on www.brightcove.com don't work in Firefox for Android and Firefox OS

You may have to create an "allow for session" cookie exception to make the Brightcove player work.

• https://players.brightcove.net

cor-el said

^: that bug is about Firefox on mobile.

• Bug 1194662 - Videos on www.brightcove.com don't work in Firefox for Android and Firefox OS

I should have noticed that.

My apologies to michaelcg.

https://players.brightcove.net/ is not meant to be used as a link, but as a domain for a cookie exception, so this exception is applied to every link to this domain embedded on a web page. This will prevent cross site (XSS) security issues (operation isn't secure).

I have finally found what seems to work in most cases. Turn Tracking Protection off. - Little icons on left of address bar. Usually has an option to turn off on the current site.