If you see the message, "Your project is not complete so it cannot be added to your cart yet," you have not finished adding photos to the project. dotPhoto prevents the printing of incomplete products so that you are not disappointed with the result.
In the example below, you can see the empty gray photo panel behind the message. However, you may also have an empty photo panel on another section of the product -- for instance, on the front or inside of a greeting card. Check all the components of your product carefully, add more photos, and then add your completed product to the cart.
If you WANT to leave a photo panel empty -- for instance, you do not want to add a signature -- upload a blank image and place it in the empty photo panel. You can use the blank signature box attached to this FAQ.