We have made some progress with this. I can now make and receive calls with the sip device. That issue now is the conference calling. I can call an extension without issue, press the conference call button and the first extension called is put on hold. However, instead of being able to dial another extension, I get a busy signal. I have to hang up the call. The first extension is still on hold and has to hang up as well. The logs from the ClearOne show that it is trying to establish the connection, it appears that the Mitel is no allowing it.