manage plan won't load

I need to set up a new xFinity account. The xFinity app tells me "account not authorized" when I try to sign in, and that I need to be a paying member. I AM a paying member with an active plan, but when i try to visit the manage plan tab on the account page of the xFinity website, the page loads forever. The "make payment" and "check bill" tabs also just lead to an "unexpected error" message. Please help, this is unbelievably frustrating.