For everyone working at home during the Coronavirus lockdown, you may be experiencing the same problem.
If your having trouble hearing any sound on a Windows 10 Remote Desktop Connection(RDP) in Firefox, this quick trick will enable sound.
Firefox has a security problem!
This is a known issue since Firefox version 56
Audio playback was disabled due to increased security restrictions.
1. Type about:config in the address bar and press Enter.
2. A warning page may appear. Click Accept the Risk and Continue to continue to the about:config page.
3. Search for the security.sandbox.content.level preference.
4. Click the grey Edit icon pencil button, next to the preference and set its value to 2.
5. Click on the “blue tick” to save the change.
6. Restart Firefox on the remote device.