I have 520 series router with CME and CUE built in it and configured one SCCP phone (CP7945) and two SIP phones (Linksys SPA 922 and CP7975).
Phones registered and are working fine. Voicemail is also configured on all of them and you can leave and listen the messages on all of them.
They all have MWI configured but on CP7975 (Cisco SIP phone, firmware SIP75.8-4-1SR1S) MWI is not working, it doesn't indicate that you have new message. When you call pilot number you can listen to the message.
Both SIP phones are configured the same way.
I also tried with the CP7911 and with firmwares SIP11.8-4-1SR1S, SIP11.8-2-1S and SIP11.8-3-1S and every time result is the same - it doesn't work.
Do u have any idea what could be the problem?