make sure both the mailbox monitor and message waiting indicator server are running on the MM server. You may want to stop and restart the serivces
Next make sure in outlook under options, voicemail tab, telephone user button, assistant tab. Make sure message waiting indicator box is checked, and verify the rule is correct. you can also set this up to light the MWI light when you get an email.
I assume you were using the outlook plugin. I guess if you use the Avaya MSS as your message store, there would still be a similar option for the light?
RTMKCEE
CM 2.1.1
Prologix R9.05
Modular Messaging 1.1