cannot refill online using chrome, safari or firefox

I've tried with 3 browsers on my Mac: with chrome, safari and firefox

I go to my account, I click on "Add funds using credit card, debit card, or checking account" link and

I am getting nothing more than empty page with link of the form

https://tmobile.ecustomersupport.com/tmobile/MyTMobileEntry.aspx?payment=CREDIT&account_type=pre&token=SOME_EXTREMELY_LONG_TOKEN&unavid=refillcard

So I am effectively unable to refill.

It was that way at least for couple of monthes.