Hi Christina, 

Welcome to Box Community and glad to help! 

We've created a new case and a member of our team will contact you through email, please keep an eye out. 

Thanks for posting!

I am getting the same message. What was the solution? 

Our issue was that we did not have enough licenses for the additional user.  It would be much more helpful if the error message communicated that, but it doesn't.  So I would make sure you have available licenses, purchase more if necessary (we actually wound up disabling a few users that no longer needed access which resolved our problem), and try again.