Hi, try this: Click the padlock icon at the left side of the address bar while you are on FB; you may be able to allow permissions at this stage, but if not, click the arrow on the right (>), then click 'More Information' and select the Permissions tab. More: How to manage your camera and microphone permissions with Firefox

If you still can't do it, try turning off any ad blocker you may be using then reload the page.

If that doesn't help, hold down the Shift key when you start Firefox to start in Safe Mode. More - Diagnose Firefox issues using Troubleshoot Mode.

If it works in Safe Mode, disable any theme or extensions you have - 3-bar menu > Add-ons > Themes/Extensions, then restart Firefox; now if it's still OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some extensions.

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

Does not work :) No Ad_blocker used.. Tried in Safe Mode.. Same Same.. Still a pop up asking me to give FB permission.. Back to "normal".. Managed to toggle permission to ALLOW CAM / MIC.. See attached picture... So facebook HAS permission (TILLATT = ALLOW) to use CAM and MIC.. But, it does not work. But works on Chrome.. ANNOYING !