Can't add mexico and canada add on, begin checkout not working

Hi guys, does anyone found the same problem? 
I've tried to add the add on to my account and when I press begin checkout nothing happens and I cant do anything. I've cleared the cache, tried 3 different browsers, incognito and nothing seems to work.. I just want to pay the 5 dollars to have unlimited service as well here in Mexico but has been a big problem. 

1st they asked a pin to register, this pin was never given out to me and finally today I’ve manage to get a phone call and solve that situation but now I cant add the add on so might find other prepaid sim card.