Discount is not applied in a bundle with a zero-price product
Some Shopify stores use products with price 0 (plus shipping) as a way to attract customers' attention.
Unfortunately, the Shopify Discount System does not allow to include these zero-price products as part of a discounted bundle.
Consequently, if you have configured the Frequently Bought Together to generate bundle discounts, they won't be applied when one of the products of the bundle has price zero.
Please note that this is a limitation of the Shopify Discount System. Our app relies completely on the Shopify Discount System to generate and apply discounts to the bundles.