I can't Sign up for 'My T-Mobile', any one could help?

I bought a new phone from hsn, it's a sumsung galaxy light. There is a sim card in the box of the phone. so I setup it in the device.

I called the service to activate the phone, he told me the phone number of this new phone.

Then I tried to sign up in the page "https://my.t-mobile.com/Login/Registration.aspx",  It sent me a temporary password by message, I input it to the page. Then it ask me to Create account password. When I inputted  my password and click "continue" button, It gone to a blank page with only page header and page footer. just like below. I don't know what's wrong and how can I register my account. Is there any one can help me?