Glitch on the website. I get that every once in a while.

I'd recommend using https.  Https://t-mobile.com

Http (non secure) allows for hijack (loopback, tunnel, vpn, hacker).

Id recommend looking at what ip the t-mobile.com resolves to on your host.  I have seen similar issues on tor vpn.

Hi @Carbohydrate Checking in on you to see if you have been able to access the website. Did either of he suggestions above help you out? if so, we would love for you to mark one as a best answer so others know what is helpful. 

Hope you have a great day!

Change your VPN location. Happens to me when using certain locations.  Not sure why.