Users on the A call server may need to re-register their phones.
This was due to a change made to fix a problem where password changes were not being applied to the A server without manual intervention. Although that problem has been fixed, it's had the side effect of invalidating existing registrations which, due to the nature of some phones, requires the users to re-register or reboot the phone themselves.
Sorry for any inconvenience.
Seems that some customers have had ongoing problems with registrations on the A server.
We're investigating.
This should be fixed now.