No ideas? I'm very surprised!!

it is not supported by my browser

Did you understand the message? Not a browser issue, FB wants you to use another browser. See the results from a search.

This must be a very recent change because it has always worked in the past!

You will have to ask FB. You should no that Mozila wouldn't want to affect so many users. That would be a very bad move. If there are no more you can mark this issue as resolved because there is nothing we can do.

Mine was working fine until the last Firefox update. Now I cannot use Messenger Video Chat.

I agree with everyone that it always worked in the past....this is something new!

How many others are having this problem? I am not finding any solutions apart from switching browsers. Has Mozilla given up the battle with Facebook?

I agree with you and it would seem so!

And now, not only FB Messenger....tonight I could not do Zoom with my daughter on a link she sent me on FB Messenger.....And again I had to go to Microsoft Edge. After many years of using Firefox, I am not so sure anymore!!