SIP phone will not register: locate the failed evidence state

Name the first missing state

Record the phone model, exact firmware, account slot, displayed state, PBX address, transport and time window without copying the secret. Confirm power, address, gateway, DNS and time before changing SIP settings. A disabled account, a REGISTER that never leaves the phone, an unanswered request and a final rejection are different failures.

Use one bounded capture or Asterisk's temporary PJSIP logger to identify the first missing message. Logs and captures can contain identities, addresses and authentication material, so restrict access, stop collection after the reproduction and retain only what the incident requires.

Registration: isolate transport from authentication

Follow REGISTER end to end

If no REGISTER leaves the phone, inspect the selected account, provisioning result and local dialer state. If it leaves but no response returns, confirm DNS resolution, destination address, port, transport, routing and firewall policy. If a response arrives, keep the full Call-ID and CSeq sequence together.

A challenge followed by a new REGISTER carrying authorization can be normal. A repeated 401 or 407 is not enough by itself to name a bad password: compare username, realm, algorithm, request URI, nonce handling and which system issued the challenge.

Prove the endpoint and auth loaded

Asterisk's PJSIP guide separates endpoint, auth, AoR, transport and contact objects. Inspect the loaded endpoint rather than assuming that a saved file or GUI form became runtime state. The endpoint should reference the intended inbound auth and AoR; the auth object should exist with the exact case-sensitive identity expected by the phone.

Do not remove authentication or reuse an administrator password to make the indicator turn green. Asterisk may return a deliberately unanswerable 401 when it cannot match an endpoint, so prove endpoint identification before rotating a valid secret.

Match the AoR named by REGISTER

For an inbound phone registration, Asterisk uses the user portion of the REGISTER To URI to locate the AoR. The endpoint must reference that AoR, and the AoR must permit a dynamic contact. A section with the wrong name, missing type, misspelled option or unsuitable contact limit can fail before credential checking completes.

Inspect the loaded endpoint and AoR and compare them with the actual To and Contact URIs. A saved endpoint without its expected AoR is not a registration-ready endpoint.

Separate binding from reachability

A successful REGISTER binds a Contact URI to an AoR for an expiry interval. That proves a current location binding, not that OPTIONS qualification succeeds, the phone rings, the call is authorized or media works. Record the contact URI and expiry, then observe at least one refresh without forcing a reboot.

If a contact appears briefly and disappears, compare requested and accepted expiry, duplicate devices using the same identity, max_contacts, removal policy, phone restarts and network changes. Do not hide the lifecycle problem by repeatedly deleting contacts.

Accept recovery in layers

After the correction, prove a fresh challenge and accepted REGISTER, the expected AoR/contact binding and a later renewal. Reboot the phone and confirm that provisioning does not restore the fault. Then test an internal call, two-way media, normal hangup and only the external destinations the endpoint is permitted to use.

This guide did not inspect a phone, PBX, credential, packet, registration, contact, call or media path. Adapt the sequence to the exact firmware, provisioning system, Asterisk build and FreePBX module state.

Follow a failed replacement flow after mobility

When registration fails only after a connectivity transition, preserve the last old-flow keepalive and the new DNS, transport and REGISTER sequence. The softphone network-change diagnostic keeps path availability, SIP flow recovery and registrar contact selection separate.

Use the Baresip branch when an account line exists

For Baresip, use the module, account and registration diagnostic. It distinguishes an absent account User-Agent, intentional regint=0 local account and failed REGISTER transaction.

Trace a Wi-Fi D810W from association to SIP response

Use the D810W Wi-Fi registration diagnostic when the phone joins the SSID but registration still fails.

Respect VoIP Much response timers before retrying

VoIP Much says repeated bad credentials and re-registration that ignores the minimum response interval can trigger source blocking. The provider-specific workflow preserves one complete transaction before credentials, timers or network policy change.

Prove the PhonerLite profile source before resetting credentials

After an update or portable move, PhonerLite may load a different sipper.ini. Use the local-state diagnostic before changing the PBX or password.

Do not reset Linphone credentials before proving the active profile

An update can expose a different configuration or user profile. The Linphone local-data diagnostic separates loaded state from later registration failure.