Skype and all other video conferencing software works. Even the test with blue jeans works and I hear audio return. Anyone else experiencing this issue? Two macs in a week both with the same problem. The bj app and mulitiple browsers all have same issue when using it.
To me this sounds like a request that should go to support. You should have those users work with support to determine the cause. They're going to want, and I would as well trying to respond to your question, more detail about the Macs. What version of OS X are they running? Do they have any other audio/video devices connected to the system? Have they gone into the System Preferences -> Sound -> Output and verified the output device is working.
It's going to be a lot easier to have support help with this I think. They can dig deeper into a call with their tools and see what is going on. If you give them a meeting ID for one you had an issue with and some details to identify the problematic system in the call, like their name they entered, they can drill down. Anytime someone tells me there is no audio or video in a single direction I immediately think firewall, but I don't know your network or where these users are connecting from. Do other devices on this same exact area of network have the same issues or do not.