I was able to fix this problem! It was frustrating how not obvious it was. The first payment has to be with a debit card for some reason (the error you are experiencing, probably). After you pay, your debit card will be added to your account. Add your credit card as a Secondary Card. Then to switch to automatic payments with a credit card, go to One Time Payment, then use your credit card to replenish your account with the minimum Replenish Amount (this depends on the person - it is defined as "Recommended based on your recent toll history" on that form). Your credit card will be charged with this amount. Then go back to Payment Methods, then remove your debit card. Your account will now use your credit card instead of a debit card.
I was able to fix this problem! It was frustrating how not obvious it was.
The first payment has to be with a debit card for some reason (the error you are experiencing, probably). After you pay, your debit card will be added to your account. Add your credit card as a Secondary Card.
Then to switch to automatic payments with a credit card, go to One Time Payment, then use your credit card to replenish your account with the minimum Replenish Amount (this depends on the person - it is defined as "Recommended based on your recent toll history" on that form). Your credit card will be charged with this amount.
Then go back to Payment Methods, then remove your debit card. Your account will now use your credit card instead of a debit card.