My embedded Youtube video links play ok in my website when the (normal/admin) viewer is viewing them in Firefox Incognito/Private window.
But the same (or even any) youtube video, don’t play in main Firefox window.
I do remember that there was some ‘Trust’ setting in somewhere in Admin Settings, under which I had to put ‘Youtube’ in ‘trusted’ list perhaps. But I’m not sure where or what that setting was.
I’ve even checked that YT embedded videos even on meta discourse don’t/aren’t playing in my FF windows normal tab.
The problem was the enhanced tracking protection of the Firefox, which was shown by a blue badge to the just beginning of the url bar, something like this:
This was discovered by me from this meta solution. As evident in this meta solution, this problem would not only stop YT videos, but also twitter links/videos etc. And may be some other external media links too. So all problems are solved now.
As soon as I turned off that protection (I’ll search for as to how can I turn off that nuisance protection for all sites, forever, in one click).