It rings staright to voicemail, but there are no messages. When I run the command locate feature extension xxxxxxx, it shows message waiting indicator as on. I did change the system option "Superset callback message cancel timer" to 1, and I think that cleared it because the next morning the light was out. I left a test message in the mailbox, the light lit. Listened to and deleted the message and the light stayed lit.
I was thinking that this issue is because the mailbox does not exist as an extension, only a single line key and it is not behaving properly. This is why I wanted to create it as a hunt group, but I cannot because it already exists and I cannot clear it. I deleted it from tel dir and remote tel dir.
This is what I see when I run locate extension xxxxxx:
LOCATE: Non prime extension number.
If anyone has any ideas and/or can better assist and wouldn't mind, I can PM you a telephone number so we can discuss it.