That setting applies just in case you have more than one required Product, if you set it to ALL then all of the required products must be added to cart to be elegible for the Promotion, otherwise, if you select ANY, just 1 of the required products must be added to cart for the promotion to be applied. Anyway we also tried that (just in case) but it didn't work either.
Taken from the help site:
If Enable Product Requirement is checked, then the promotion will only apply discounts to the product(s) listed here. To add products, enter a search term and then check off the ones you want to apply to the promotion. The list can be set to require All (every checked product must be in the cart before the promotion will apply) or Any (as long as one checked product is in the cart the promotion will apply). If a value is set in the Require Quantity field, the customer would need to have that many of the required product(s) in the cart to obtain the discount.