The products are a membership (new or renewal) to our organization, and donation to the organization. The store does not ship or download anything to the customer for these two products. "Product is Virtual" is set to "yes". "Always free Shipping" for one product is set to "yes", the other is set to "no". I suppose both products should be set to "yes". The error appears for both products.
Additional info: I have reported this problem on Zen Cart Github as issue
#4528. A possible fix that works for me is posted there, as well as other settings. Checkout is through the normal route, selecting PayPal on the payment method selection page. I do not display the PayPal express button.
Bookmarks