> ## Documentation Index
> Fetch the complete documentation index at: https://docs.retellai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Debug outbound connection issues

> Diagnose `not_connected` outbound Retell calls — work through `invalid_destination`, `no_valid_payment`, carrier blocks, and other disconnection reasons.

When an [outbound call](/deploy/outbound-call) has a status of `not_connected`, the call never established a connection to the destination number. The `disconnection_reason` field tells you why. This page covers the `not_connected` reasons; for the full list of reasons across all call statuses, see [debug call disconnection](/reliability/debug-call-disconnect).

## Disconnection reasons for not connected calls

* `invalid_destination`: the destination phone number is invalid. It may contain spaces or invalid characters, or your telephony provider requires a specific format (such as E.164).
* `telephony_provider_permission_denied`: the SIP trunk authentication failed.
* `telephony_provider_unavailable`: the telephony provider is unavailable or returning errors.
* `sip_routing_error`: there are loops or other issues in the SIP routing.
* `marked_as_spam`: the call was marked as spam. See the root cause and remediation below.
* `network_blocked`: the dialed number's carrier network blocked the call — commonly the carrier's spam filter. See the root cause and remediation below.
* `user_declined`: the user explicitly declined the call.
* `dial_failed`: no SIP error code is available, or the error is unknown.
* `dial_busy`: the number dialed is busy.
* `dial_no_answer`: the number dialed did not answer.

## Steps to troubleshoot

<Steps>
  <Step>
    Check the call history and detailed log. It contains the disconnection reason, the error message and optionally a **[SIP error code](/reliability/debug-calls-pcap#common-sip-response-code-reference)**. If the logs contain a SIP error then you can see the details by checking the PCAP file available in the call logs — see [Debug calls with PCAP](/reliability/debug-calls-pcap) for information on how to debug using PCAP files.
    In most cases, this would be enough for you to identify the root cause.

    <img src="https://mintcdn.com/retellai/a1LftRqc_k-5TDA7/reliability/images/pcap_download.png?fit=max&auto=format&n=a1LftRqc_k-5TDA7&q=85&s=9419cf630d085b11a262ef73d1f293c7" alt="Call log detail with the PCAP file download link for a not_connected call." width="608" height="692" data-path="reliability/images/pcap_download.png" />

    <Note>
      PCAP files are only available when the agent's data retention is set to **Everything** and the SIP transport is **UDP/TCP**. Calls using TLS transport or any other data retention setting will not have a PCAP available.
    </Note>
  </Step>

  <Step>
    If the call detailed log and PCAP file do not provide enough information, you can try the following:

    * If using custom telephony
      1. In **Phone Numbers**, select the imported number, open the **…** menu, and choose **Edit Phone Number Settings**.
      2. Check the termination URI, transport, and credentials, then use [Test SIP Connection](/deploy/custom-telephony#test-your-sip-connection). Correct any errors and click **Save** to apply changes.
      3. Retry the call. If the connection test succeeds but the call still fails, check your provider's logs for call routing or destination restrictions. The connection test does not place a call.

    * If using numbers purchased from Retell
      1. Make sure the destination number can accept the call. Currently, numbers purchased from Retell can only make calls to US numbers.
  </Step>
</Steps>

### Number marked as spam or blocked by the carrier network

Both `marked_as_spam` and `network_blocked` mean the carrier stopped the call from completing; `network_blocked` specifically means the destination carrier's network (often its spam filter) rejected it. The root cause and remediation are the same.

When a number experiences a high outbound call volume spike without any warmup, and/or has a low pickup rate, it might be marked as spam by carriers. When this happens, the number will get blocked frequently. To remedy this, you can try to:

* Purchase a new number, and warm it up before pouring all traffic to it (slowly add outbound traffic to it)
* Increase the pickup rate, read more at [Increase Pickup Rate](/build/telephony/call_efficiency_overview)
* Register the number with our spam remediation feature, read more at [verified phone number](/build/telephony/verified-phone)


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