This issue occurs when a user tries to log in to a phone configured for Cisco CallManager Extension Mobility and enters the user ID and Personal Identification Number (PIN).
The Error 0 error message requires that you ensure the neccessary Cisco CallManager Extension Mobility services are running. To resolve this issue, verify that all Cisco CallManager services are running. If not, start the services. Refer to Control Center for information on viewing the status and to start and stop Cisco CallManager services for a particular server in a cluster.
For information on how to activate or deactivate services from the service activation web pages, refer to Service Activation .
For other related information, refer to these documents: