iPad roaming in Canada - unable to login to my TMobile account

Travelling in Canada with a TMobile prepay sim in my iPad that I use for data only. I need to add additional credit but no matter what I try, I am unable to login to my T Mobile account. 
 

I login successfully and then get asked to enter a 6 digit number that will be emailed to me because I am in an international location. I enter the number and then get asked to enter my sims cell number. I do this and then get told there is a T Mobile ID and to login.

This process then repeats and repeats and repeats in and endless loop and I never actually get to be logged in.

T Mobile app simply returns something went wrong all the time.

HELP!