My environment: UCM 8.6.1, CUP 8.5.1, CUPC 8.5.3
I have encountered an error on CUPC saying "Device initialization error has occured. ". Everything is working except the softphone and hardphone mode. It seems to be something is wrong on the UCM side.
The root cause of my problem is when the UCM is installed, it is synchronized with a NTP server with wrong time configured, therefore the tomcat certificate on UCM is expired. The step to fix this:
1. UCM OS admin page > Security > Certificate management
2. Find the tomcat.pem, click on the certificate and check the validity date
3. If it is expired, click on "Regenerate"
4. Restart the tomcat service in CLI - "utils service restart Cisco Tomcat"
After CUPC logout and login, the softphone and hardphone mode works again!