I am going through the "T2: Ecommerce" training module prior to taking the C2 certification. In "Tutorial 2: shopping cart & checkout" (https://doc.dynamicweb.com/training/t2-ecommerce/t2-ecommerce-marketing-implementer/2-2-shopping-cart-checkout#5273) I have set up the shopping cart, and added a product to it. After filling out the name and address informations and so on, when I click "Place order" - I am being sent back to the "Show cart" step, instead of being sent forward to the "Receipt" step. Also, no order is being placed in the backend, no matter how many times I go through the steps and click "Place order". Am I missing something here? Do I have to activate something, that is not written in the tutorial? And how do I find out, what is wrong with my checkout flow?