CAN NOT PAY MY BILL ON LINE ANY LONGER WHY??????????

That's why.  I'm in the same boat you are, though mine is through Direct Express.  Hughesnet evidently have a policy in which they don't accept prepaid cards, though it wasn't enforced until very recently.  

Hopefully the old site will continue to work, as when no longer does, we will be back to calling them to make a payment, and I, like you, HATE giving my CC info over the phone.  

Hopefully, also, they are looking into making exceptions to the rule for those like us.