Hi Andrew, 

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

Can you try clearing your browser cache and then try this again and 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!

Regards,

Thank you -- clearing the cache (in FireFox) did allow me to input a phone number (in XXXXXXXXXX format).

I have succeeded in setting up the 2FA via SMS.

Hey, Andrew!

I'm glad to hear that you're all set now and successfully set up your 2FA.

Thanks for reaching out and stay safe!

Regards,