Go to the Alternate Extensions page for that subscriber and add his second extension. If these are two lines on one phone, you're fine with just this. If you have a second phone that you need an MWI light to come on for, go to the Messages screen and hit Add, and add another MWI extension.
Hello - I saw this thread and immediately thought about CallManager 3.2 and above. If you are integrating Unity with CCM 3.2 and above, check your CallManager System Policy for setting the MWI light - the default is to light the primary line appearance only. You can modify the Message Waiting Lamp policy on an individual DN to "Always Light" for all extensions.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.