401 is often an authorization or authentication error. Either something in the info provided isn't meshing with the data on the account, or something with the scripting itself isn't passing through properly on the backend.

Double check all the info for the card, if all is indeed correct then check with the bank (they could be rejecting the transaction--sometimes happens with international transfers).

If everything checks out on your end and the bank's end, then it may be something on the backend...open a formal ticket with SE through the support portal about it.

Oh yeah... sometimes a failed transaction can block an instrument from being accepted for a while. You could be stuck in a 24/48/72 hour holding cycle, depending on how many times it has been rejected and such.