Core Issue
It is possible to upgrade from Cisco CallManager 4.x to Cisco CallManager 5.0 as long as the hardware requirements for Cisco CallManager 5.0 are met.
Resolution
Refer to the Upgrading Cisco CallManager section of Upgrading Cisco Unified CallManager Release 5.0(1) for more information.
Refer to License File Upload in order to obtain and upload the license file for Cisco CallManager 5.x.
For more information on upgrade related issues, refer to the following TAC cases.