500 from Retell on Inbound SMS

Support Help
1

Hello,

Background

I recently configured a number for SMS following these instructions:

I am using Twilio with an Elastic SIP Trunk and a number that is in a messaging service connected to a “Verified” A2P campaign. I’ve done the “SMS Add-On”, associated the number to the same agent for inbound / outbound, and created an inbound webhook.

The Bug / Error

I am able to initiate an outbound chat to myself without any errors - I receive the message I would expect to from the agent. However, when I respond to this message, it does not appear in the chat history and I never get a response.

I’ve narrowed the issue down to an ERROR: 11200 in Twilio. I can see a POST request to https://api.retellai.com/twilio-sms-webhook/org_hJfQIvKGkbWArtkE that receives a 500 Internal Server Error back from Retell with no other details that I am able to view.

What I’ve Tried

  1. I’ve double checked the configuration of my SIP Trunk. I did find that I had originally not enabled “PSTN Transfer” so I enabled this.
  2. I confirmed that my number was in the messaging service connected to my verified A2P campaign.
  3. I confirmed the Termination URI for the number was added correctly within Retell.
  4. Since I had made many attempts, I tried ending all of my previous chats in case multiple chats at the same time with the same number was causing an issue.
  5. I purchased a new number, added it to the A2P campaign’s messaging service, reconfigured after trying all of the above with the previous number, and still get the same issue.

Can I get more insight into what the details of that 500 internal server error are? If helpful here are some of the chat IDs from my testing. Most of them should have received multiple “Test” and “Hello” messages:

  • chat_a593fc7009957ac183268759ae8
  • chat_3073ac942eda3369899a6519b98
  • chat_1b61b33b78025ebcb610b7e818a

Thanks in advance for any help!