Retell AI Common Errors Overview Quick reference for the top Retell AI errors and their solutions. Prerequisites - installed - API key configured Instructions Error 1: 401 Unauthorized Fix: Verify API key in Retell Dashboard. Ensure starts with . Error 2: Call Fails Immediately Fix: Use E.164 format: . Both and must be valid. Error 3: Agent Not Responding Fix: Check LLM configuration: Error 4: Function Call Timeout Fix: Your function endpoint must respond within 5 seconds. Offload heavy work: Error 5: Webhook Not Receiving Events Fix: Set on the agent, not just in Dashboard settings: Error 6:…