To follow up for others reading this thread, I emailed customer service and they responded by telling me to reach out to their billing department by calling 941-360-3990 and selecting the accounting option.
I spoke with someone in accounting and it sounds like they had trouble with the card number I provided at submission. Not sure why, but doesn’t really matter. Anyway, I gave them the card number again over the phone and they were able to process the payment. It was for the amount of the invoice minus the collectors club fee, as they had promised, even though it didn’t show up on the invoice that way. I was told since payment has now been received the cards would be placed in queue for shipment.
Seems like it’s probably going to work out ok. Just wish there had been more information and communication at the start so that we could have resolved it faster.