MiCollab 8.1.2.8 with AWV Conf 8.1.2.7-1.
Some users  are unable to get into an audio only meeting.  Sometimes users will hear ringing with no answer.  Sometimes a fast busy.  Same dialing external number or internal. 
19 ports configured. Usually have 10 users in the meeting, I do get an acs alert at the 9 ports in use threshold.  “9 ports in use 10 ports are free”.
Not sure where to start looking… Anyone experienced similar? 
On the PBX (MCD) I have seen this entry in the logs, but don’t know if this is relevant to the issue. 
 ProcessRenegotiationMsg[Answer] TransId[a640132 2e18aa3] Unexpected: No MSGNegotiator exists with Key[29f93f39], nothing left to do.
Thanks for any direction.