The 601 error use to be because your bank info and your SE account info are not matching in some way. For me it was because my bank (card) info had my middle initial and my SE account did not. Unfortunately you can not update your name on your SE account but luckily for me I work for my bank that has my card and asked a co worked to take my middle initial out and voila.

Other thing that may not be matching could be your address check for any small difference between your SE account info and your bank info
If you notice SE when adding a CC doesn't have you type in your name and address like most companies would so this is where most of the hang ups would be.