Only the automatic personalization items will show a preview.
That is by design. Any manually personalized items will not have a preview, because the system can't create a preview. Manually personalized campaigns are those where either more than two fields are needed, or where a field may contain many words or allow the customer to upload a photo. In those cases, T-Rex cannot create a preview. What happens in manually personalized products is this: The user enters their information and adds to cart. When the order is placed, the order does not go directly to PrintTech, it comes to you. You then have to put the text into the picture file (using Photoshop or other image editing software), save it and then send the CSV file to PrintTech.