Shipping cost excluded from coupon value

Hello,

I got the following problem:

Gift Certificates are working, but only for the items in the basket and not for the shipping cost.

Example:
Gift Certificate for €10


Basket 1 Item €6,50
Shipping Cost €4,90
Total €11,40

Coupon entered gives -€6,50 which leaves a total of the Shipping for €4,90
Why is the Shipping not taken into account? Should be a total of €1,40 after entering the above gift certificate of €10

I use the standard shipping module. AWO Coupon Pro version 1.3.6
Could a template be the problem? If yes, which file should i look into?

has it been working before? You should first take a look in awocouopon->installation check to make sure everything is installed.