Hi there, 

Welcome to the Box Community!

I understand that one of your users encountered an error when logging in to Box via your SSO.

I checked your profile for this post and I see that it is linked to a Personal Free account, and SSO is not supported on those with Personal accounts.

If you have an Enterprise or Business account, I recommend logging in to that account, and submit a support ticket for this issue so that Product Support team can help investigate.  

Best regards,