You shpuld check the user's manual of your cantral, starting with the queston if it supports this function. If don't have a manual, you can look for one online using Google search for MANUAL, NorStar Phones and THE MODEL
the buttons are not programmed properly. Use 'feature * 0' to see what is on the buttons. press feature * 2, press the key, then dial the extension #. this will program the key with the proper extn #
"Q: My Norstar Startalk, Flashtalk, or voice mail says my mailbox is not accepting any more messages. I deleted all my messages, but callers still cannot leave a message. Why?
A: Check with your voice mail administrator. Chances are another Mailbox on the system used up all the message storage space. Usually it's the general delivery mailbox that hasn't been checked for messages on a regular basis."Frequently Asked Questions
The following discussion suggests that voicemail can be inactivated, and cab be re-activated by logging in and pressing '4'
Startalk Flash Won answer Nortel Phone System Tech Support
This says that the mailbox must be initialized.
http://www.uniquecomm.com/docs/Startalk_Flash_Quick_Reference_Guide.pdf
I would just COPY the settings from another extension that is the closest or same as what you want...
F**CONFIG ... Terminals&Sets ... (enter "good" extension #) ... COPY softkey ... (destination extension) ... System&User ... and you're done.