I'm running the cart version 3.93.0 on dnn 05.03.01 (7) www.chuckswoodbarn.com. When you go to a product details page, and then click on the add to cart button, it does not work. I verified this on the www7 protal.
I just applied a hotfix to the www7 test site but had to reset the cart settings let me know if you can recreate the error. If all looks good to you we can publish the hotfix.
It seems to be fixed. As a developer I can understand having bugs, but the add to cart button? It must be too close to the holidays :).