I have spent a couple of hours to check the product “157 Carton”. When WooPOS sent product listing request to the WooCommerce API, all products showed up except this product. This is the only one missing. I’m not sure why, it could be API issue or other WordPress plugins. I created a duplicate copy of this product, nothing changed, the copy of the product showed up.

To fix this problem, you can just create a copy/duplicate, delete the original product, and import all products again.