Express checkout
Apple Pay, Google Pay, Shop Pay or PayPal buttons send the customer straight to checkout. Panaché checks the rule at checkout: an incomplete order is blocked, even through these buttons. The customer then sees your message.
Tip: hide express checkout buttons on your product pages (a theme setting). Customers then go through the cart, where the gauge guides them before paying.
Without Shopify Plus
Shopify doesn’t allow checkout pages to be customized. The customer sees Panaché’s error message, with the allowed pack sizes and a link back to the cart.
With Shopify Plus
With Panaché’s Plus plan, the gauge also shows in checkout, with the missing bottle addable in one click. Add the block from the checkout editor (Settings > Checkout > Customize).