Calls placed but not connecting: a first-things-to-check guide

Your dialer is placing calls, the channels light up, the counters move — and yet almost nobody is reaching a live person. Before you blame the lists or the agents, the truth is almost always sitting in the response your carrier sends back for each attempt. Every outbound call gets a SIP response code, and that code tells you exactly where the call died.

What is actually happening

A call placed over a SIP trunk is a short conversation between your dialer and the Carrier. Your box sends an INVITE; the carrier answers with a numeric status — a SIP response code such as 200, 486 or 503. A 200 means the call was answered. Anything in the 4xx, 5xx or 6xx range means it was rejected or failed before a human ever heard a ring. If the connect rate is near zero, you are looking at one code repeated thousands of times, not random bad luck.

sequenceDiagram
  participant D as Dialer
  participant C as Carrier
  participant P as Person
  D->>C: INVITE outbound call
  C-->>D: 100 Trying
  alt accepted
    C-->>P: ring the number
    P-->>C: answer
    C-->>D: 200 OK connected
  else rejected
    C-->>D: 4xx or 5xx no person reached
  end

Where to look

Two reports give you the per-attempt picture. The Dial Log Report lists every call placed by a server over a day or date range, separated by SIP response code, with the lead ID, server IP, outbound caller-ID, SIP hangup cause and reason for each one. The Carrier Log Report shows all dial attempts and their response codes going out of your system, and lets you download the raw logs. Start in the Dial Log so you can see which code dominates.

Check these in order

1. Pull the Dial Log Report for the last hour and note which SIP response code repeats most. One code dominating means one root cause.
2. A flood of 403 Forbidden or 401 usually means the carrier is rejecting your outbound caller-ID or the source IP is not on their allow list. Check your CID (caller ID) and confirm IP authentication on the trunk.
3. 488 Not Acceptable Here points at a media mismatch — the carrier and your box cannot agree on a Codec. Make sure the trunk offers what you send, typically G.711 ulaw, and drop exotic codecs.
4. 503 Service Unavailable or repeated 5xx means the carrier side is overloaded or out of capacity. Slow your call pacing and contact the provider before you burn the list.
5. Calls that show 200 OK but agents still hear silence are an answer-supervision problem: the carrier marked the call connected before a real person answered. That belongs in the SIP Event Report rather than here.

Work the code, not the symptom. If the Dial Log says 403 across the board, no amount of fresh leads will help — the carrier is shutting the door. Once you know which code dominates, the fix is usually a single change to the trunk, the caller-ID, or the codec offer. For the wider method, see the troubleshooting playbook, and to go deeper on the report itself read how to read the Dial Log Report. If you would rather not babysit a self-managed install while you chase this, VICIfast runs the box for you.