BT have a nationwide, system wide problem. They are treating it as a P1 (Priority 1) response their highest level incident.
Status Updates can be seen at the following link:
We’re aware of a problem that means some of our customers are unable to receive incoming calls through their fibre home phone connection. We’re sorry about this but our engineers are working hard to get this fixed as quickly as possible.
Anthony Caddy said:
“Our back up service is in place, however if you are a BT client you may not be able to divert to us due to this being a National problem. Please contact your supplier for more help.”
We apologise for any inconvenience this may cause and we are doing all we can to get back online with BT.