Hi, I have the similar issue on the CME.One of 7911 phone is registered in cme but their was no dial tone. Just removed and re-added the ephone-dn, it fixed the issue. cme(config)#no ephone-dn xxcme(config-ephone-dn)#ephone-dn xxcme(config-ephone-dn)...

Try Upgrading the Firmware of the Phone. I think this is a known issue in DX650 and Firmware upgrade will surely help. Thanks,  Bilal