Why are the discount code boxes not displaying on the checkout page?
Why are the discount code boxes not displaying on the checkout page for products with Custom Pricing discounts?
If you are using Custom Pricing in a discounting method / version that creates draft orders, discount codes can't be used as Shopify's draft order checkout does not support them. If you want to allow your customers to use discount codes, you can switch to a Custom Pricing version that supports it. These are:
Standard Method (V2) with Shopify Functions enabled supports the use of discount codes in the native Shopify Checkout. Read more about this in Shopify Functions for Custom Pricing (Standard Method).
Accelerated Method (V3) allows your customers to use specific types of discount codes on the cart page. Read more about this feature in Discount Code Stacking in Custom Pricing (Accelerated Method).
For more information, please visit Discount Methods and How to Switch.