There could be a number of reasons why SMS may sometimes not work. One of which is if you are using an MSISDN that starts with +883. To check your MSISDN, navigate to the "SIM" tab in the EUI.
If you have confirmed that your MSISDN starts with +883, please raise a ticket to email@example.com and we will update the MSISDN for you.
For more troubleshooting regarding SMS issues, you may refer to the related KB articles below.