I can’t play audio on a Remote Desktop Connection
If you are on a Remote Desktop Connection (RDP) on Windows, audio playback will be disabled due to increased security restrictions. This is a known issue since Firefox version 56 that we are working hard to fix.
In the meantime, you can reduce the sandbox security level by following these steps:
In the address bar, type about:config and press Enter.
The about:config “This might void your warranty!” warning page may appear. Click I accept the risk! to continue to the about:config page.
Search for security.sandbox.content.level, double-click on the preference and set its value to 2.
Restart Firefox on the remote device.