Our company has a NEC sv8100 system it has been operating good for the past six years. We use the mobile extension feature extensively. We recently changed providers for our PRI from Logix Communications to AT&T. Before the change the desk phone would ring once then both be desk phone and the mobile extension would ring. Since the changeover in the PRI the desk phone now rings Twice and stops ringing and the call is forwarded to the mobile extension. Voicemails cannot be left on the NEC phone system since the call is not redirected back to the phone system. Any ideas?

How many mobile extensions?
How many are having this issue, 1 or all?

Did a NEC certified tech come out for the PRI cut over?
Did he or she make any program changes?

We have a total of 136 extensions with about 50 setup with mobile extensions. All are having the same issue.

I highly recommend calling in a NEC SV8100 certified tech.
This could be as easy as re-booting the system or something a lot deeper.

I have tried to reboot the system. when we call our provider I was told that the SV8100 was end of life and I need to upgrade to the 9100 to get service.

I'm guessing how they deliver the PRI is a little different than your last provider. Just for giggles try putting a # (pound) at the end of the tel number for the mobile extension. Your 8100 should still have support on it through your NEC dealer if they are any kind of dealer.

Gary