Browser / Version: Firefox 76.0
Operating System: Windows 10
Tested Another Browser: Yes Chrome
Problem type: Site is not usable
Description: Browser unsupported
Steps to Reproduce:
According to Guillermo (https://support.mozilla.org/es/questions/1283313), Firefox does not support Facebook group video calls, even supporting the necessary protocols to support it. Only Firefox and Edge (EdgeHTML) are affected by this. However, the Chromium-based or WebKit-based browsers do not have any problems.
View the screenshot

Browser Configuration
_From webcompat.com with 鉂わ笍_
Thanks for the report, I was able to reproduce the issue.

Tested with:
Browser / Version: Firefox Nightly 76.0a1 (2020-04-02)
Operating System: Windows 10 Pro
Moving to Needsdiagnosis for further investigation.
We have a bug open https://bugzilla.mozilla.org/show_bug.cgi?id=1390729 and Adam has contacted Facebook regarding this
This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue at https://webcompat.com/issues/new if you are experiencing a similar problem.
Most helpful comment
We have a bug open https://bugzilla.mozilla.org/show_bug.cgi?id=1390729 and Adam has contacted Facebook regarding this