Rules Work on the Product Page but Not the Cart

Test the cart directly

Add the product, then try to submit a quantity below the minimum, above the maximum or outside the configured step.

Check cart customization

Some themes and cart extensions replace WooCommerce cart quantity components or use custom AJAX endpoints.

Check for conflicts

Temporarily disable other quantity, cart or checkout customization extensions on staging and retest. If the behavior changes, another extension may be intercepting the quantity update.