I’ve set up a virtual extension and a virtual mailbox to go with it but none of the standard notification methods that a phone uses to inform me of a new voicemail actually work.
So the red light at the top right of the phone doesn’t appear and nothing flashes either on the Voicemail Line Key. (The voicemail message is there and can be accessed though).
Try this.
On an unused key program it as a BLF with *98XXX where XXX is th emailbox number of the mailbox you want to monitor. when a message is in that mailbox the BLF sill show up and you can use it to dial the VMbox and get the message