Quick answer
Bundle discounts fail when cart contents do not match rules, discounts conflict, shoppers bypass widgets, or Shopify Functions are disabled. Work through eligibility, then widget path, then combinations.
- Widget path matters for Kitforge QB/FBT.
- Check line properties on orders.
- Test one discount at a time.
- Readiness errors block activation.
Eight causes in order
Start with the simplest: is the discount active, are the right variants in cart, did the shopper use the widget, are functions enabled, is max sellable exceeded, are segments excluded, is another discount winning, is the offer paused.
Work the list top to bottom — most merchants fix the issue before step five.
Widget-only discount failures
Quantity breaks and FBT often require add-to-cart through the widget. If the shopper uses the theme's default button, checkout may show full price.
Reproduce in incognito and inspect cart line properties for _kitforge_* keys.
Combination and stacking
Disable other automatic discounts temporarily. Re-enable one at a time to find conflicts. Shopify combination settings matter for Buy X Get Y plus product discounts.
When to contact support
If readiness passes, embed is active, widget path is correct, and checkout still fails — capture cart JSON, offer ID, and theme name for support.
Final recommendation
Most failures are eligibility or path — not broken Shopify.
If you want this kind of offer to feel native to the buying journey, Kitforge Bundles is built around that exact problem: turning related Shopify products into clearer bundle offers before the shopper reaches checkout.
FAQ
Discount shows on PDP but not checkout?
Often widget-only mismatch — customer added SKU outside the widget.