If the light is on with no messages you can use the message retrieval in the Prologix to determine what turned on the light:
In the Prologix you can program "Stations with System-wide Retrieval Permission" .Enter the extension that you want to retrieve the LWC messages from
On the same station, put the following buttons:
cov-msg-rt
delete-msg
next
From that extension press the cov-msg-rt button, enter the extension that has the LWC message, press next, then press the delete-msg button. This will tell you which extension turned on the light. This may help you to determine if it is a voicemail problem or not.
You can also turn the debug log on in the Octel 100 to help you track problems. It also may just be a port problem in the Octel 100. My company still supports Octel 100's so if you need help or more information let me know.
Chuck