I have tried the MWI refresh.  It does work sometimes but the light comes back on.

If you do a 'debug ccsip messages' and trace a extension to extension call inside the UC520 and dont answer, and let the call go to voicemail and then leave a message (when you finish the message and deposit it, watch the trace).

Here I dialed extension 204:

//-1/xxxxxxxxxxxx/SIP/Msg/ccsipDisplayMsg:
Received:
INVITE sip:A800204@10.1.10.2:5060;user=phone SIP/2.0
Via: SIP/2.0/UDP 10.1.10.1:5060;branch=z9hG4bKOFWElJ61UWE5ysYeA5w1kw~~104
Max-Forwards: 70
To:
From: <401>;tag=cue9ac5a240
Call-ID: 1246996875853155@10.1.10.1
CSeq: 1 INVITE
Content-Length: 172
Contact: <401>
Content-Type: application/sdp
Cisco-Gcid: 56CE4A4D-0122-1000-4000-001125CUCE68
Call-Info: <10.1.10.1:5060>;method="NOTIFY;Event=telephone-event;Duration=2000"
Allow-Events: telephone-event

Look to see the TO field in your invite going to 10.1.10.2 (CUE loopback).  Is it A8002XX to turn it on?

In the case you traced retrieving a voice mail, as soon as you delete the message and the light goes off you will see

A8012XX in the debug message:

//-1/xxxxxxxxxxxx/SIP/Msg/ccsipDisplayMsg:
Received:
INVITE sip:A801204@10.1.10.2:5060;user=phone SIP/2.0
Via: SIP/2.0/UDP 10.1.10.1:5060;branch=z9hG4bKOFWElJ61UWE5ysYeA5w1kw~~105
Max-Forwards: 70
To:
From: <401>;tag=cueadb96d4e
Call-ID: 1246997058905157@10.1.10.1
CSeq: 1 INVITE
Content-Length: 172
Contact: <401>
Content-Type: application/sdp
Cisco-Gcid: 56D11559-0122-1000-4000-001125CUCE68
Call-Info: <10.1.10.1:5060>;method="NOTIFY;Event=telephone-event;Duration=2000"
Allow-Events: telephone-event

Now look at what was discussed in this thread above.  Another Partner gave you something to check.  The two Ephone-DNs that should have the number A801... for MWI OFF and A800... for MWI ON.

Make sure yours look like that.

We have seen cases where the CUE gets out of synch with IOS/CME and in one place they are set to A8xx and in the other place just 8xx and this will cause MWI inconsistency. If your trace shows a Invite to 800... and 801... then that can be assumed to be built wrong in CUE.  That can be fixed, but requires a session in CUE and a few more CLI commands in there.

Is your CUE (10.1.10.1) matching like this one does:

What is your situation in terms of dial peers and trace evidence?

The traces show A800xxx and A801xxx.

I checked the CUE config.  It had A801 and A800.

ccn application ciscomwiapplication aa

parameter"strMWI_OFF_DN" "A801"

parameter"strMWI_ON_DN" "A800"

The ephone-dn's mentioned by the partner are there but not the dial-peer.

I just realized I typed WMI instead of MWI in the subject line.

So are you receiving the SIP invites as shown in Steve's example, but the light remains on?  Or when you tested and saw the A801... invite did the light turn off?  If you isse the "show dial-peer voice summary" you should see dialpeers with destination patterns A800... and A801...

What version of firmware do you have on the 524 phone?  Is the 524 phone a member of any voicemail groups?

Earlier versions of the 524 phone had MWI lighting up for GDM's as well.  I believe the current version of the 524 phone only lights up for the primary ext.

The firmware is 8-1-12.  I will upgrade to 8-1-16b.

The software is upgraded.  Problem still remains.  I guess a couple more things to try are different model of phone or making the user a totally different extension.

I would recommend opening a TAC case at this point.  You could also resync the MWI now that you have upgraded the firmware.