Hi Tristan.

You may be hitting this caveat:

CSCdu79519

Voltage might be too low for Message Waiting Indication (MWI) lamps on some phones.

Some older phones that use MWI lamps might not light up, even if the VG248 port is configured to indicate Message Waiting with the Lamp setting. To check this setting, go to the following path from the Main screen:

Telephony > Port specific parameters > MWI type

This problem arises because MWI lamps require a line voltage greater than the maximum voltage that the VG248 can supply.

If you suspect that your lamp MWI should be lit, check the configuration of the port and the status of the messages in your mailbox. If the configuration is correct and you have a waiting message, you should try replacing the phone with one of a similar type to confirm that your phone is not faulty. If the lamp still does not light, you probably have a phone that cannot have its MWI lamp lit by the VG248. Other phone functionality is not impaired by the lamp deficiency.

The only workaround to this problem is to consider replacing your phone. Test the new phone before committing to a large purchase.

-Adam