The Watering Hole

I'm at my wits end with this. For some reason Firefox will not play an embedded Youtube clip (it says "an error occurred, try again later)  but if you go to Youtube, no problem. Any ideas? No, I'm not interested in going to Chrome.

Try allowing third-party cookies.  

It was suggested by someone on the Mozilla support forum that I delete youtube cookies. This I did. Actually I deleted all cookies. It worked!