Checkout page is locked by Shopify, we are not able to modify the checkout page as a 3rd party app, therefore Discount Mixer codes are not available on the checkout page.
- We do not support discount codes at checkout. Discount Mixer widget exists prior to checkout either on a cart page, drawer, or popup. A discount code is generated that combines the values of the applied discounts to use at checkout so entering another code will replace that value.
- To avoid confusing customers, you can change the wording of the discount box at checkout to say “Gift card only” by navigating to Shopify Settings > Languages > Change Theme Language > Checkout & System > Gift card and discount title/label/placeholder. This is a video instruction if you prefer that.