The web site does work reliably. However, I did finally locate an issue with it not wanting to work on cellular. You may want to check and see if you're issue is the same. When I access Gas Buddy at home, there is no Wi-Fi for miles, and Gas Buddy behaves properly. However, when there is a public, open Wi-Fi available, and I am not connected to it, it does not want to work. It wants me to connect in order to be able to use the "free" data. Once I turn OFF the Wi-Fi, it starts working again.
I have that same issue with other apps as well, where things don't work reliably if I'm on a "border" of a Wi-Fi signal, where the signal is showing connected but too far away to connect properly. Cortana also fails me in these circumstances, though, so it may not be your issue.