Error: Invalid product:
1- Is your customization page defined as homepage?
2- Is your customization page defined as one of woocommerce pages?
3- Does the product you are trying to customize exists and is published in your shop?
4- Are you accessing this page from one of the product designer buttons? You're trying to access the customization page whitout a product to customize. This page should only be accessed using one of the customization buttons.