I'm hoping someone out there that can help me. I have a very old avaya phone system and PBX. The message waiting light does not come on when there is a voicemail message. The interface that I have is at least 20 years old. None of the research that I have foundis relevant to a phone system from 1994 or 1992. Does anyone out there know how to turn on or activate the message waiting indicator for this 20 year old system?