Here's how to successfully enter a discount code:

On a computer: after you have accepted the terms and conditions and entered your contact information in the next step, a summary of the products in your order will open on the right side of the page. Below the products there is a section: "Discount code or gift card code". Enter the discount code in that box and click "Apply" next to it. The discount should now be reflected in the price.

On mobile: after you have accepted the terms and conditions and gone to the contact information section, at the top of the page, just below the Saaren Taika Shop text, you will see the section "View order summary", click to open it and enter the code in the "Discount code or gift card code" box. Then click the arrow button on the right side of the box. Now the discount should be reflected in the price.