When creating a USPS label you may get the error below.
Please check with your credit card company. This can happen if the charge was declined for some reason.
Call the credit card company and ask the reason for the decline. Once that is resolved, it may take 24 hours for the credit card to allow more charges.
If you must buy labels immediately, try changing the credit card on file: https://shipleap.freshdesk.com/a/solutions/articles/48001216184