Product selection checkboxes missing when creating a coupon

Product selection checkboxes missing when creating a coupon

I’m using WP Express Checkout 2.5.3. When creating or editing a coupon and selecting “Specific Products Only”, the product names are displayed, but the checkboxes next to the products are missing, so it is impossible to select any products.

I also checked the page HTML. The product checkboxes are not merely hidden by CSS — they are not generated in the HTML at all. The only checkbox present on the page is wpec_coupon[active].

This feature worked correctly before updating the plugin. I can provide a screenshot if needed.