Thank you for reaching out to the Community! I apologize you were unable to prepay as easily as you should. What browser are you using? Does trying a different browser allow the button to appear? In cases where the submit button is missing from the payment screen, we suggest contacting our Billing Support directly to process a payment manually. However in your case I can see you were able to successfully prepay your account after all! Please let us know if there is anything else we can assist with in your account.