If the alert message does not display on the product page or cart page, check the following causes in order.
The alert message only displays when a value falls outside the limit set on the rule. For example, if a product quantity rule limits quantity to 2–5, the message displays when you try to add 1, or 6 or more, to the cart.
With "Checkout only", the alert message does not display until you proceed to checkout, even if you are outside the limit. If you want it to also display on the product page or cart page, change the display timing for the rule to "Cart updated and checkout".
Alert messages on the online store are displayed through the theme's error display handling. If the theme is not implemented to receive and display errors from the Cart and Checkout Validation API, the alert message may not display, and Shopify's default error screen or a blank screen may appear instead. Even in this case, orders that violate the limit are still blocked at checkout.
Follow these steps in order.
(1) Update your current theme to the latest version
(2) Enable "Show alert message in modal" under "Settings" in the app admin
(3) Change the display timing for each rule to "Checkout only"
(4) If this does not resolve the issue, ask your theme provider to support displaying errors from the Cart and Checkout Validation API
Note: Enabling "Show alert message in modal" also displays errors from other apps or the theme in the modal, even when they are unrelated to this app's limits. For details, see the "Alert Message" article.
If the problem persists after checking the above, contact us through the inquiry form. For our investigation, please let us know the title of the rule, the URL of the page you checked, and the name and version of the theme you are using.