Hi James, 

Welcome to the Box Community, I'm happy to help!

Please make sure to follow the steps in this article on setting up 2 FA with SMS: https://support.box.com/hc/en-us/articles/360043697154-Multi-Factor-Authentication-Set-Up-for-Your-Account

Please make sure to choose the correct country you are in and enter your complete phone number (no spaces or special character) on the required field and click 'Continue', and a confirmation code will be sent to the phone number you entered. Enter the code you received as a text message then click Submit.

Thanks for reaching out and let us know how else we can help!

Best,