### Answer --- I don't have specific information about Verizon's call forwarding code format in the available sources. The Retell AI documentation mentions that you should configure call forwarding through your telecom provider's portal or by dialing specific codes, but it doesn't specify the exact format for Verizon. [(1) ]() For the correct Verizon call forwarding code format, I'd recommend checking Verizon's official documentation or contacting their support directly—they'll be able to confirm whether to include the country code (+1) or not. What the sources do confirm is that once calls are forwarded to your Retell AI number, that number should be in E.164 format (e.g.,

"+14157774444"

with the country code) . [(2) ]() Check out these potentially useful sources: - [Call Forwarding for AI Voice Agents]() - [List Phone Numbers]()

​ To learn more, see the sources I considered: [[1] Call Forwarding for AI Voice Agents | Retell AI](https://www.retellai.com/blog/best-practices-for-setting-up-ai-voice-agents-with-call-forwarding) [[2] List Phone Numbers](https://docs.retellai.com/api-references/list-phone-numbers) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer --- The endpoint path is correct. The Get Concurrency endpoint is: [(1) ]()

GET /get-concurrency

Your full URL ` should work, though the documentation shows the path as

/get-concurrency

without explicitly showing the

/v2

prefix. Headers format: [(2) ]()

Authorization: Bearer YOUR_RETELL_API_KEY

Response includes: [(1) ]() -

current_concurrency

- the current amount of ongoing calls -

concurrency_limit

- total concurrency limit -

base_concurrency

- free concurrency limit -

purchased_concurrency

- amount already purchased -

concurrency_purchase_limit

- max purchasable -

remaining_purchase_limit

- remaining purchasable amount Example response:

json
{
  "current_concurrency": 10,
  "concurrency_limit": 100,
  "base_concurrency": 20,
  "purchased_concurrency": 80,
  "concurrency_purchase_limit": 100,
  "remaining_purchase_limit": 20
}

​ To learn more, see the sources I considered: [[1] Get Concurrency](https://docs.retellai.com/api-references/get-concurrency) [[2] API Key Overview](https://docs.retellai.com/accounts/api-keys-overview) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer ### Answer To help troubleshoot, I need more details. Could you share: - The error message or disconnection reason from your call history? [(1) ]() Common disconnection reasons for failed outbound calls include: | Reason | Description | |--------|-------------| |

invalid_destination

| Destination phone number is invalid | |

dial_failed

| SIP error codes not available or unknown error | |

dial_busy

| Number dialed is busy | |

dial_no_answer

| Number dialed did not answer | |

marked_as_spam

| Call marked as spam by carriers | |

telephony_provider_permission_denied

| SIP trunk authentication failed | |

user_declined

| User explicitly declined the call | Troubleshooting steps: 1. Check the call history and detailed log for the SIP error code and error message 2. If using **custom telephony (Twilio/Telnyx) **: - Verify your SIP trunk configuration is correct - Check with your telephony provider for errors on their side - For Twilio: ensure you have a verified customer profile and the number is assigned to it [(2) ]() 3. If using **Retell-purchased numbers**: - Confirm the destination number can accept calls (US numbers only for Retell numbers) [(1) ]() 4. If getting

no_valid_payment

or KYC errors: - Complete the KYC verification in your dashboard [(2) ]() Please share the specific error/disconnection reason and I can provide more targeted guidance.

​ To learn more, see the sources I considered: [[1] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) [[2] OUTBOUND CALLS FAILING](https://discord.com/channels/1186424376300679209/1370279738081542215) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

@AI Evy - Not Found Body Download { "status": "error", "message": "Not Found" }

### Answer ### Answer A 404 Not Found error on outbound call creation typically indicates an issue with your phone number or agent configuration. [(1) ]() Most common causes: 1. Phone number not properly configured — Your

from_number

must be a phone number you've purchased and configured through Retell AI. You can't use arbitrary numbers. , [(2) ]() 2. Incorrect parameter names — Use

override_agent_id

instead of

agent_id

, and

retell_llm_dynamic_variables

instead of `custom_data`: [(1) ]() , [(2) ]()

json
{
  "from_number": "+16504144521",
  "to_number": "your_target_number",
  "override_agent_id": "agent_71724df7636716ceb3a7e244c8",
  "retell_llm_dynamic_variables": {
    "name": "Sarah"
  }
}

[(1) ]() , [(2) ]() 3. Agent binding — The phone number should have an

outbound_agent_id

configured, or you need to use the

override_agent_id

parameter in your request. [(1) ]() , [(2) ]() To verify/fix: - Confirm your

from_number

is a Retell-purchased or properly imported number - Check that the phone number has an

outbound_agent_id

set - Verify your agent ID is correct and the agent exists under your API key [(3) ]() Could you share: - The exact endpoint URL you're calling? - Whether you purchased the

from_number

through Retell or imported it?

​ To learn more, see the sources I considered: [[1] 404 Error on Create a Phone Call](https://retell.discourse.group/t/404-error-on-create-a-phone-call/22) [[2] Here is how that can be fixed](https://retell.discourse.group/t/here-is-how-that-can-be-fixed/23) [[3] Agent exists and is published, but API returns "Found agents: 0"](https://discord.com/channels/1186424376300679209/1392892371313754164) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer ### Answer The

"Authorization header required"

error means your API key is missing or incorrectly formatted in the request headers. [(1) ]() Required header format:

Authorization: Bearer YOUR_API_KEY

Common issues to check: 1. Missing header entirely — Ensure you're including the

Authorization

header in your request 2. Incorrect format — The format must be

Bearer YOUR_API_KEY

(note the space after "Bearer") , [(2) ]() 3. API key validity — You can create a new API key in the dashboard under Settings > API Keys [(3) ]() Example for Create Phone Call: [(2) ]()

javascript
import Retell from 'retell-sdk';
const client = new Retell({
  apiKey: 'YOUR_RETELL_API_KEY',
}) ;
const phoneCallResponse = await client.call.createPhoneCall({
  from_number: '+14157774444',
  to_number: '+12137774445',
}) ;

If you're making raw HTTP requests (not using the SDK) , make sure the header is included exactly as shown. A user with similar 404 issues resolved them by creating a new API key. [(7) ]()

​ To learn more, see the sources I considered: [[1] API Key Overview](https://docs.retellai.com/accounts/api-keys-overview) [[2] Create Phone Call](https://docs.retellai.com/api-references/create-phone-call) [[3] Manage API Keys](https://docs.retellai.com/accounts/manage-api-keys) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer ### Answer Based on your description, the webhook determined the structure during the initial test but isn't triggering on subsequent calls. Here are key things to check: Retell webhook behavior: [(1) ]() - The webhook has a 10-second timeout - If no success status (2xx) is received within 10 seconds, it retries up to 3 times - Webhooks trigger in order but are not blocking — if

call_started

fails,

call_ended

can still trigger Common issues to verify: 1. Make.com scenario status — Ensure your Make scenario is active/turned on, not just saved. After determining the structure, you typically need to activate the scenario for it to listen continuously. 2. Webhook URL placement — Confirm the webhook URL is configured at the correct level in Retell (phone number or agent level) . [(2) ]() 3. Call connection — If the call did not connect (e.g.,

dial_failed

,

dial_no_answer

,

dial_busy

) , the

call_started

webhook will not be triggered. However,

call_ended

and

call_analyzed

webhooks will still fire. [(1) ]() 4. Response from Make — Make must return a 2xx status within 10 seconds or Retell will retry. Check Make's execution history to see if requests are arriving but failing. To troubleshoot: - Check Make.com's scenario execution history for incoming requests - Verify your Retell call history shows the call completed successfully - Confirm which webhook event type you're listening for (

call_started

,

call_ended

, or

call_analyzed

) Which webhook event are you trying to capture — call started, ended, or analyzed?

​ To learn more, see the sources I considered: [[1] Webhook Overview](https://docs.retellai.com/features/webhook-overview) [[2] Personalization with Airtable]() ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

### Answer Could you share the specific error message you're receiving? To help troubleshoot effectively, I need: 1. The exact error text (e.g., 404, 403,

dial_failed

,

invalid_destination

, etc.) [(1) ]() 2. Where the error appears — Is it from: - The Retell API response? - Your Make.com webhook? - The Retell call history/detailed logs? 3. The disconnection reason from your call history, if applicable Common outbound call errors include: , [(2) ]() | Disconnection Reason | Meaning | |---------------------|---------| |

invalid_destination

| Destination phone number is invalid | |

dial_failed

| SIP error codes not available or unknown error | |

dial_busy

| Number dialed is busy | |

telephony_provider_permission_denied

| SIP trunk authentication failed | |

marked_as_spam

| Call blocked by spam filter | To check: Go to your Retell Dashboard → Call History → click on the failed call → view the detailed log for the SIP error code and disconnection reason. [(1) ]() Please share the error details and I can provide more targeted guidance.

​ To learn more, see the sources I considered: [[1] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) [[2] Deprecating on 6/30/2025](https://docs.retellai.com/deprecation-notice/6-30) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.