Problem statement
We have a had a number of users today report having problems with their SMS coming through. We use Auth0 to authenticate on our site with Twilio as the SMS provider. I do not know if this is an Auth0 issue or a Twilio issue. The error message says “We couldn’t send the SMS. Please try again later”. The users are in the UK and are using a mobile phone number. Do you know what can be a reason to it?
Solution
Network operators in the UK have made a change and will no longer support messages sent to UK users from international long codes. They will begin to block SMS messages that are sent using international long codes (note that domestic long codes are still supported). The change is effective as of 00:00 GMT, June 1, 2023.
Unfortunately as of now there is nothing that we can do to change or “fix” this. You will need to go through your SMS delivery provider to get support.