Coupon campaigns can only be used in US Currency.
Hope this was helpful! Any other questions don't hesitate to reach out.
Helpful in the fact that it answers the question, very unhelpful in the fact that it doesn't support other currencies!
It seems that there are quite a lot of features of CC that are only supported for US users, yet users in other parts of the world are paying the same level of fees.
I apologize for the inconvenience. I can see how this feature can be very important to you and will relay this feedback to our engineers.