Want to use gift certificates for the next order

-- url of the page with the problem -- : blue-ocean-wassersport.de/gutschein
-- HikaShop version -- : 4.0.1
-- Joomla version -- : 3.9.1
-- PHP version -- : 7.2.10
-- Browser(s) name and version -- : all browsers
-- Error-message(debug-mod must be tuned on) -- : no error message

Hi,

I created with hike serials gift certificates, which I sell to my customers. The spart works.

But when the customer wants to use the code, it do not work....

What have I do, to make the right configuration?

Any idea?

regards

Harry