Another small integration issue when connecting Call Manager Express with Lync 2010, users in a response group were getting thrown an error when the call arrived from the PSTN via our CME SIP trunk.
The Lync error this time was slightly less informative “Cannot complete the transfer, when contacting your support team, reference error ID 503 (source ID 239)” or see below for the graphical version.
After a bit of digging this was related to our trunk configuration being misconfigured when it came to how SIP refer messages were being handled. This was caused because in essence the Lync server had picked up the call to play our messages, music whilst waiting etc. before transferring it to a real human which is where the problem starts, the real human cannot now transfer the call to another person.
After doing some digging I found a TechNet article describing my exact symptoms (http://support.microsoft.com/kb/2506083), the problem occurs when you have “enable refer support” switched on.
To resolve you need to go in to your trunk configuration and remove the “enable refer support” check box as below, the GUI will also fail to save you configuration unless you also remove “enable media bypass” so un-tick that as well.
This will leave you with a trunk configured similar to the below.
Once completed press OK and then select commit all in the next screen to save and activate your changes within Lync. Again as with any changes grab a cup of coffee and leave Lync for 5 minutes so that it processes your changes.
That is it, your response group transfer issues should now be sorted.