Firefox - videos will not play sound

We are a Thin Client shop. Users connect to one of 4 Server 2012 R2 RDS servers via RDP. For several weeks I have been battling an issue with Firefox not playing audio for youtube (and other) videos. The problem is plaguing all of my RDS servers.

Remote audio IS working because affected users can watch the same videos through Internet Explorer.

I have uninstalled and reinstalled Firefox. I’ve updated Flash player. What’s next?

The odd thing is that MY Firefox will play video/audio while signed in with my “least user” credentials. So, since I’m not signed in as Administrator, I don’t think it’s a credential issue but it could be a windows profile issue…or maybe a Firefox profile issue.

It doesn’t appear to be the Thin Clients because my boss connects to RDS with a Windows 7 PC and he too is plagued.

I’m hoping someone else has tamed this beast…

as an user with elevated permissions could FF be set to a different audio output? I’ve see that happen on many of my windows 10 devices.

I was experiencing the same issue when RDPing to my Windows 10 machine.

Following this article resolved the issue for me: