Rec'd email saying my credit card isn't good for...

Just order again with the correct details. The renewal will use the last used details.

That is weird. You should be able to order, even when your subscription has just been renewed (which it hasn't).
Where does it say that? What part of the process?
regularlabs.com/purchase/cart/add/modulesanywhere

I don't store any credit card info on my site. When you purchase, the payment platform creates a mandate that allows it to charge your credit card again. I can only see the last 4 digits of your CC.

Please try to order again, and let me know where and when you get an error. Preferably with screenshots.

You can use the 'Confidential information' button in the forum editor to hide sensitive information.

Ah, ok: so you can first switch of automatic renewals here:
regularlabs.com/subscriptions

Thanks for your purchase ?