Same thing here. I was able to sign in to a payment update screen, got a message that overdue balances had been paid (which, I'm guessing, is the waived April fee), but now when I try to sign in, I am directed to a reactivation screen. When I log in, I get the following message: UCS-5024. Invalid Process. Please exit the current application.

Seems as if on some accounts the process to waive April made the payment system think balances were not paid instead. Sigh.