This occurs when the user is logged into an Extension Mobility phone with Cisco IP Manager Assistant (IPMA). The Extension Mobility DN number is 2000, for example. The user logs out of Extension Mobility and back in. Calls to 2000 fail, and the calling side hears continuous ringing.
This can also occur if the user logs into Extension Mobility and select the IPMA service. If you just log out of Extension Mobility so no active phone is using a DN 2000, calls should go to voice mail as the profile DN is set up. But the calls never go to voice mail and the calling side phone rings continuously.
To resolve this issue, restart Tomcat service and Computer Telephony Integration (CTI) services.
For information on restarting Tomcat service and CTI Services, refer to these documents: