Could be a DNS issue. I believe the CCM best practice is to use the CCM IP Address instead of server name (in the Enterprise parameters Services Url). Here is some good info for troubleshooting this issue;
Fixing Problems with IP Phone Services
If you confront an issue where you cannot access any IP phone services from your IP phone or, if you receive the error message Host not Found when you press the Services button on the IP phone, you might have problems with the Services URL. The Services URL might contain your server name or the wrong IP address. Therefore, your IP phones cannot resolve and access any services.
SIP traces provide key information in troubleshooting SIP Trunks, SIP
endpoints and other SIP related issues. Even though these traces are in
clear text, these texts can be gibberish unless you understand fully
what they mean. This document attempts to br...
Please find the attached HTML document, download and open it on your PC.
This provides an easy to use form where you simply answer a few
questions and it will render the proper jabber-config.xml file for you
to copy/paste. There is built in logic to verif...
CUCM Database Replication is an area in which Cisco customers and
partners have asked for more in-depth training in being able to properly
assess a replication problem and potentially resolve an issue without
involving TAC. This document discusses the bas...