We have faced a problem, recently we have migrated to a CUCM9 we simply import our config to the CUCM (after solving its problem), after switching to new CUCM we had issues with some phones, hence we deleted the configuration security trust list and ITL file, after this the phones started to be registered but we lost some services like Voice mail (the button), Directories and phone designer services.
To check the problem I tested another phone which had not the same issue, I deleted the security trust list and bang the same problem appeared.
I do not understand what is the problem I tried
New Firmware and old Firmware.
I tried factory reset
Do you still have all your URLs under phone URL parameters and under Secure Phone URL Parameters?
I had faced this type of problem with 6945 IP Phone, but I got it resolved by installing latest device pack in CUCM. So 1st check the URLs in phone parameter as suggested by Hermanus and after that you can try installing latest device pack.