Does the app support multi-currency?
Behind the scenes, Checkout Promotions leverages Shopify's order editing feature. Because Shopify does not support multi-currency with order editing, this app is unable to support multi-currency. This means that only orders placed in your store's default currency is eligible for a promotion. For example, if your store is USD but a customer checks out with EUR, they will not see a promotion but if your store is EUR and a customer checks out with EUR, they will see a promotion.