https://prepaid.t-mobile.com does not open when connected to a vpn service

Hello! I have both post-paid and pre-paid accounts with T-crap. I use a vpn service to secure my internet connection. When I try to connect to my prepaid account, I get a "request timed out" error. If I disconnect from vpn, it lets me connect to my prepaid account! Why? Is it T-Crap that won't let me connect? Or is it my VPN service blocking my connection to T-crap because there are malware and/or phishing codes onboard the T-mobile's websites (pre-paid and post-paid)??. This is frustrating.