I've ordered from the Lye Guy a number of times with no problems, but I haven't ordered in the recent past.
A problem with completing a payment might be an issue on their end. But I have to say, speaking as a small biz owner who accepts credit card payments, that it's often a problem at the customer's end.
Have you tried paying with another credit card, PayPal account, or other accepted payment method? If you only have the one credit card, have you checked with your credit card company to ensure the card is active and functional?
If it looks like everything is working on your end, then I'd contact the Lye Guy directly to discuss the issue.