SMS MFA fails to send with error: "The 'To' phone number: +***, is not currently reachable..."

Problem statement

We have a user that has MFA via text message enabled but we are getting the response in the logs:

"provider_error": {
"errorCode": 21612,
"message": "The 'To' phone number: +**********, is not currently reachable using the 'From' phone number: +************ via SMS."

But the phone number is completely valid. We have an enterprise account and we send messages via Twilio and this user cannot login to our platform which is affecting service. Please can you advise why are we receiving this message?


This is actually an error message that Twilio is sending in response to the SMS attempt. Here is Twilio’s documentation regarding this error type:


There are instructions found on that page to help troubleshoot this issue including reviewing possible sender ID restrictions and formatting issues. As this is an error on Twilio’s end, unfortunately we are unable to provide much more specific support in regards to this issue and we would recommend reaching out to Twilio support for further help in fixing this if the troubleshooting steps do not help resolving the issue.