Hello Ronald,
It would be best if you could provide additional information in order to better understand why doesn't the MWI turn on and why the message on the trace.
-Is this a new configuration?
-Is the problem for one user?
-How does your network design look, example is there any firewall between CUCM and CUC or the phones?
-Is it only turning on or also off?
-Can you dial the On and Off extension?
-Were any changes made previous to experience the issue?
-Do the Application logs reveal any additional information?
-Is this a SCCP or SIP integration?
-Is this working along with a SIB integration?
-DaRoPe