So, the ability for a buyer to leave a product review is tied to a listing's MPN or UPC (or whatever other universal identifier is available). I checked just a couple of your listings, and you've indicate the MPN or UPC "does not apply;" therefore, your listings will not feature the product review option.
Here's an eBay help page of product review FAQs. You'll want to expand the question "What listings are eligible for reviews?"
Product Reviews