flat-fuchsia
flat-fuchsia•5h ago

Call connects but AI doesn't speak - transport timeout after 3-4 seconds

Hey team, I'm having an issue with outbound calls where the call connects and rings, but the AI never speaks. Here's what's happening: The Issue: - Call goes from queued → ringing → connects - After Twilio trial message plays, there's a 3-4 second silence - Then call drops with "Customer Did Not Answer" or transport error - The AI never gets a chance to say the first message What I've tried: - Removed duplicate greetings from system prompt - Switched between "assistant speaks first" and "user speaks first" modes - Used both phoneNumberId and raw Twilio credentials - Verified Twilio Account SID and Auth Token are correct - Phone number is active and configured in Vapi Setup: - Using Twilio integration (trial account) - Outbound calls via API connected through n8n - Assistant has firstMessage configured - Call status shows as ringing in API response but never progresses to in-progress Call logs show: - Status: ringing then times out - "Customer Did Not Answer" (but I'm answering the call) - Sometimes: call.start.error.get.transport I've attached screenshots of: 1. Call logs showing the error 2. Assistant configuration 3. API response showing call status Is this a known issue with Twilio trial accounts? Or is there something wrong with my transport configuration? Thanks!
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1 Reply
Vapi Support Bot
Vapi Support Bot•5h ago
Suggestion:
Double-check that your API request includes both a valid assistantId and phoneNumberId—missing or incorrect values for these fields can cause the AI not to speak, even if the call connects. Here’s a sample JSON body for the API call: 
{
  "assistantId": "your-assistant-id",
  "phoneNumberId": "your-twilio-number-id",
  "customer": { "number": "+1XXXXXXXXXX" }
}
{
  "assistantId": "your-assistant-id",
  "phoneNumberId": "your-twilio-number-id",
  "customer": { "number": "+1XXXXXXXXXX" }
}
Make sure these IDs match the ones configured in your Vapi dashboard. This is a common cause of silent calls and transport errors according to the documentation and community support. Sources: - Discord Community Support Example - Vapi Outbound Calling Documentation
⤵️ Mention @Vapi Support Bot for follow-ups 🐥

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