We had this same issue when trying to do PIN sync in CUC 12.0(1).
Trying to enable PIN sync in CUC and clicking save,it failed with - Failed to send message to remote AXL server. Please check error log for more details.
This is how we fixed it, in case anyone working on a similar issue
Enable Micro traces on CUCM . Database & Admin Service>Axl web service. Recreate problem. Pull logs and it will indicate the issue. In our case it was the huge list of user template that we had in Unity connection. For some reasons, CUC was sending the complete list of templates to be inserted into a table when AXL server was being updated. This was a big list and we were seeing: "A quoted string exceeds 32768 bytes" for the insert
We deleted some user templates and tried to Enable PIN Sync.It worked fine.
Although Cisco Docs indicate you can create unlimited number of user templates.This will cause you issue when you update AXL server or try to enable PIN synchronization in CUCM and CUC. Something to keep in mind.
