You require min. CUCM version 7.1(2) to support 6945.
Please refer the datasheet.
Signaling protocol support
The phones are supported on Cisco Unified Communications Manager and Cisco Unified Communications Manager Business Edition Versions 7.1(2) and later, compatible with both Skinny Client Control Protocol (SCCP) and Session Initiation Protocol (SIP
Please let me know what is the number of DLU it is showing for 6945.