Resolution
After a Cisco CallManager upgrade, the Softphones must install the latest telephony service provider plugin from the Cisco CallManager server. To do this, log in to the Cisco CallManager and choose Application > Install Plugins > Cisco Telephony Service Provider.
The other common reason for no lines appearing on Softphone is a username or password configuration issue on the Softphone client. To resolve this issue, refer to Verifying Username and Password Specification for Cisco IP SoftPhone Client Configuration.
For more information, refer to Installing and Configuring Cisco IP SoftPhone on the Client PC.
