Debug why a Retell call disconnected

Open the call in Call History or retrieve it with the Get Call API to find its disconnection reason.

Call detail page in the Retell Dashboard showing the disconnection reason for a call.

Diagnosing disconnection reasons

Find the reason in the table below, then follow the fix. For deeper diagnosis of specific cases:

not_connected outbound calls (dial_failed, invalid_destination, spam blocks, and other SIP failures) — see debug outbound connection issues.
SIP-level signaling and media — inspect the call’s PCAP file, covered in debug SIP calls using PCAP files.

When a phone number makes many short calls in a short period, carriers might mark it as spam. The number then gets blocked and shows up as dial_failed.

Disconnection reason	Call status	Description
`user_hangup`	ended	Expected behavior, user hung up the call.
`agent_hangup`	ended	Expected behavior, agent hung up the call.
`call_transfer`	ended	Expected behavior, agent transferred the call.
`call_take_over`	ended	Expected behavior, a human took over the call from the agent, which permanently stops the agent for that call.
`voicemail_reached`	ended	Expected behavior, if the agent is configured with voicemail settings, and voicemail is reached.
`ivr_reached`	ended	Expected behavior, if the agent is configured to hang up when encountering an IVR system, and IVR is reached.
`inactivity`	ended	Expected behavior, call was terminated due to the “end_call_after_silence_ms” setting reached after long inactivity.
`max_duration_reached`	ended	Expected behavior, call was terminated due to maximum duration reached.
`dial_busy`	not_connected	Outbound call not connected, the number dialed is busy.
`dial_failed`	not_connected	Outbound call not connected, dialing failed with no or unknown sip error code.
`dial_no_answer`	not_connected	Outbound call not connected, the number dialed did not answer.
`invalid_destination`	not_connected	Outbound call not connected, the number dialed is invalid. Can be due to spaces or invalid characters in the number. Or it can be your telephony provider requiring a specific format (like E.164 format).
`telephony_provider_permission_denied`	not_connected	Outbound call not connected, the sip trunk credentials are not authenticated.
`telephony_provider_unavailable`	not_connected	Outbound call not connected, the telephony provider is unavailable.
`sip_routing_error`	not_connected	Outbound call not connected, the sip routing is going over too many hops or is in a loop.
`marked_as_spam`	not_connected	Outbound call not connected, the number dialed is marked as spam. See Spam Likely Overview.
`user_declined`	not_connected	Outbound call not connected, user declined the call.
`concurrency_limit_reached`	error	Error, concurrency limit reached, add a retry with exponential backoff. Or consider enterprise plan.
`no_concurrency_fallback`	ended	Inbound call could not get a concurrency slot and was transferred to the configured fallback number.
`no_valid_payment`	error	Error, no valid payment registered on file, or service shut down due to bill overdue.
`scam_detected`	error	Error, scam detected for that particular agent.
`error_llm_websocket_open`	error	Error, LLM websocket did not open between Retell server and your backend. Likely because the Custom LLM URL is incorrect or your LLM server is unreachable. See custom LLM troubleshooting.
`error_llm_websocket_lost_connection`	error	Error, LLM websocket connection broke during the call. Often a missing `ping_pong` echo or a host idle timeout. See custom LLM troubleshooting.
`error_llm_websocket_runtime`	error	Error, LLM websocket received a closing signal other than `1000` from your server.
`error_llm_websocket_corrupt_payload`	error	Error, LLM websocket received unspecified payload, such as a binary frame instead of text.
`error_no_audio_received`	error	Error, has not received audio from Twilio or web frontend for a while after connection has established.
`error_asr`	error	Error, Retell’s ASR encountered a problem.
`error_retell`	error	Error, unspecified Retell side problem.
`error_unknown`	error	Error, unknown error.
`error_user_not_joined`	error	Error, user did not join web call within 30s after calling startWebCall.
`registered_call_timeout`	error	Error, phone call is 5 minutes or more apart from registration.

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Debug call disconnection

Diagnosing disconnection reasons

​Diagnosing disconnection reasons

Diagnosing disconnection reasons