Hello @Iain Westwood, this is currently a known issue. Please create a ticket so you will be contacted once it's resolved.

Any progress or resolution? I have a few users with the same sporadic error.

Hi there, we're still experiencing this issue. How can this be resolved?
If it can be a ticket, surely the answer can be posted here as well so admins can use it.

Hello - I'm experiencing this issue as well. How can this be resolved? I only need to access the keypad function on the RC app to enter a 4 digit pin, so my Cisco AnyConnect VPN will allow my access to my system(s). A temporary "override the microphone settings" would do the job I believe.

I am also experiencing the same issue. Microphone is not blocked in settings. Have created a ticket but have had no response. Please advise a workaround to get this working.

Did you guys happen to find out a solution, I am facing same issue on a HP laptop running window 10 pro. Everything was going great, it was working fine but when we came back last Monday it started showing same error. At first it said the same on headsets but It started working on headsets somehow when I tried to fix it. 
Can you help me to fix it so ring can start working without headset?