Why are discounts / promotions not displayed in the store?

In many cases, the problem lies with the rule builder or the rule that was set. The easiest way is to put a product in the shopping cart and check whether the rule of the Rule Builder is applied there. This is because the Shopware standard function is used and is independent of our plugin. If no discount appears in the shopping cart, then there is a problem with the rule of the Rule Builder and therefore the set rules to check.