I tried to buy your "Got Inflation" stickers from them and my card gets declined and it works everywhere else today.
You can also order directly from the company we use to print ours.
https://www.stickermule.com/u/4c84ba884f9c3ae
They get cheaper the more you buy.
Discussion
Strange, are you sure your billing info is correct?
And did you try contacting your bank or support?