This is driving me mental!!  

I've programmed the SIP trunk over to Lync as per the MOL guide and I just can't get it to work. I'm pretty sure the calls are hitting the Lync server but then my 5224 desk phone just shows busy.
          Active Rejected   Non-Auth Calls     Auth Calls       Auth Failures
Profile    Calls   Calls  Incoming Outgoing Incoming Outgoing Incoming Outgoing
     Lync      0        4        0        2        0        0        0        0
    Total      0        4        0        2        0        0        0        0
There are 1 SIP link(s) programmed.
Link       Lync state is       IN SERVICE (link down count 0) 
I now get the above. The output is showing calls as either Rejected or Non-Auth. When I'm dialling 4222 from my mitel desk phone (which is the dial in conf number on lync) it's coming as non auth. Is there a security setting I'm missing??