Why Does Webhook Return 401 for Retell AI but Not for ReqBin?

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1

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Webhook returning 401 for Retell AI but works for ReqBin
I have an HTTP webhook workflow that returns 401 ["Unauthorized"] when called from Retell AI’s servers, but works perfectly when tested from ReqBin.
Authorization: set to “None”
HTTP Response: “Return HTTP 200 OK”
ReqBin test: 200 OK ✓
• Retell AI webhook: 401 ["Unauthorized"] ✗
The bracketed ["Unauthorized"] response appears to be from Pipedream’s infrastructure, not my workflow code. I’ve tried creating multiple new workflows with fresh URLs and the same issue occurs.
I’m on the paid Basic plan. This is blocking my product launch. Can someone from Pipedream help? Happy to share the workflow URL via DM.

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Hey, a couple of things to check out. Can you asses Retell AI doesn’t block traffic from AWS? Pipedream runs on aws east

are you on a plan supporting VPC? if so, i’d recommend trying with an static IP Egress traffic from Pipedream

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Thanks Sergio. I’m on the Basic plan ($45/month), no VPC configured.
I don’t believe Retell blocks AWS traffic - their function calls (custom functions during calls) hit my other Pipedream workflows successfully. It’s only the global webhook that fails.
Also, I tested by changing Retell’s webhook URL to webhook.site (completely separate from Pipedream) and webhook.site received nothing - while Retell’s logs still showed 401 errors. This suggests Retell might be caching the old Pipedream URL and not actually sending to the new URL I configured.
I’ve also opened a ticket with Retell about the potential URL caching issue.

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In Pipedream, are you using like a “http trigger” to start a workflow? then in Retell, are you registering the trigger’s URL as the webhook URL? mmm, I’d say in this case, double check you are not setting up the trigger with authorization enabled

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Yes, I’m using an HTTP trigger to start the workflow. The trigger’s Authorization is set to “None” - I’ve verified this multiple times and even created brand new workflows with fresh URLs to test.
Here’s what’s strange: I can share my workflow URL with you via DM and you can test it yourself from ReqBin - it will return 200. But when Retell sends to it, it gets 401.
Would it help if I shared the workflow URL privately so you can look at it directly?

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Thank you! handing off to

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sounds good, thanks!

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Hi Could you please send an email describing this issue to support@pipedream.com?
That way, we’ll be able to access your account details, investigate the webhook behavior more thoroughly, and keep the communication centralized to help you more efficiently.

9

Sounds good, doing that now!

10

Just sent the email with all the information, let me know if there is anything i missed.

11

sorry i might not have gone through, having a dns problem, i should be able to resend it in a couple minutes

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email just went through, let me know if you need anything else!

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Which email address did you use to send this request? I haven’t been able to find it yet.

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sorry i just saw this message, the email should be hq@taskiva.ai

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Update: Retell support confirmed they ARE sending the request to my Pipedream URL (https://eo12anwqexl4e5c.m.pipedream.net) and receiving a 401 ["Unauthorized"] response back.
My workflow has Authorization set to “None” and HTTP Response set to “Return HTTP 200 OK”. The workflow works fine when tested from ReqBin.
Can you check on your backend why this specific URL is returning 401 to Retell’s servers? There must be something at the infrastructure level blocking these requests.
Call ID from Retell: call_6862a2dc56eb00074dc279b6430 Timestamp: 2026-01-22 16:09:56 UTC

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I’ll look into this, thank you.