Flat discount is for a currency other than that of the subscription

You are attempting to apply a flat discount that has a different currency to that of the subscription

Error Message	`Flat discounts must be in the same currency as the subscription. Discount currency: %s, Subscription currency: %s`
Error Code	`subscription_invalid_discount_currency`
Status Code	`400`

Common causes

The flat discount you are trying to add to the subscription has a different currency code than the subscription itself

Ensure the currency code on the discount provided matches that of the subscription