Phone makes calls but cannot receive them

Use a controlled incoming call

Call the extension internally first, then call its public route if it has one. If internal delivery fails, the carrier is not the first suspect. Note whether the PBX attempts to send an INVITE to the handset.

Inbound and outbound routing are separate

Inspect the destination and contact

Verify that the extension is the actual destination after schedules, forwarding and group rules. Inspect the stored contact address and whether it reflects the current network path. A phone can send outgoing requests through NAT while an outdated contact directs incoming requests elsewhere.

Check for duplicate account use and unexpected contacts. Another device registered to the same identity can affect where a call is delivered depending on PBX policy.

Inspect handset behavior

If the INVITE reaches the phone, check do-not-disturb, local forwarding, account activation and the response it sends. A silent ringtone or headset setting can make an alerting call appear undelivered. Compare the phone's call history with the PBX record.

Confirm persistence

Repeat delivery after a handset restart and after enough time to exercise registration renewal. Test a call through the public number as well as the direct extension. Do not solve stale contacts by allowing unlimited registrations without understanding the account design.