Error 21211 for a valid phone number


One of our user tried to sign up with a valid phone number like this:
+33694XXXXXX (france country code) and we had a 21211 error (invalid phone number).

The number is in fact totally valid so we don’t understand what the problem can be, it is the first time since we had this problem after lots of successful sign-ups with the same formatting.
The only specifity is that the owner of this number lives outside of France, could that be a problem ?

If anyone has an idea on this matter, please let me know !

Thanks a lot

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Hi @bhamon-dot

The 21211 error you’re seeing comes directly from Twillio:

Invalid ‘To’ Phone Number

You attempted to initiate an outbound phone call, but the Called phone number you supplied was not a valid phone number or was incorrectly formatted. Twilio accepts phone numbers in E164 format: [+] [country code] [subscriber number including area code] .

Can you double-check if the number is properly formatted according to the E164 format and check the possible solutions in the twillio page linked above?

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Hello @ricardo.batista and thank you for your answer.

I checked the phone number with the regex in the twilio doc : ^\+[1-9]\d{1,14}$
And it comes out valid. So I still don’t understand what’s wrong.

Here is a fake number with exactly the same format : +33601234567

We also know this number is valid because manual calls get through


That error is coming directly from Twillio, Auth0 does not parse it and just forwards the error. You can try checking the phone number directly in the Twillio lookup service, using

As an example, looking up +33601234567 I get:

“caller_name”: null,
“country_code”: “FR”,
“phone_number”: “+33601234567”,
“national_format”: “06 01 23 45 67”,
“carrier”: null,
“fraud”: null,
“add_ons”: null,
“url”: “

Thank you for your answer, as you pointed out twilio thinks this number is incorrect.
This is probably a specificity of France DOM/TOM numbers (Oversees France)

With these numbers the country code (+33) is not really accurate, it is just mapped to the real country code by carriers to have a seemless experience for all french numbers. The original country code for this number is different and should be accepted by twilio. We have to internally develop support for this on our frontend.

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