Xoom Help Center
Why do I see the message “Payment Source not valid”?
This might indicate a wrong bank account or routing number, wrong credit or debit card number, or simply that any other information previously provided for that payment source is not valid.
If you still want to use the same funding method, please remove (delete) it from your Xoom account and then re-enter it, creating a new funding source with the corrected information. You might have to contact your Bank or your Credit Card institution if you are not sure where the error lies.
You can also simply choose another payment source of your choice to complete your transaction.