I'm having a hard time figuring out what form is being used when clicking on the print icon from the item fulfillment form that was created from a Sales Order. I'm an admin, I checked the linked forms under the Sales Order and it's all blank, but when I check the advanced pdf forms for packing slip it looks nothing like the one when I click on the print icon of the item fulfillment. I even tried making small changes and saving to see if it was it, but nothing. Can someone help to solve this?

First go to Customization > Forms > Transaction Forms. Find the ticked default Packing Slip. Edit that transaction form to determine which layout is being used. Possibly it’s not configured for advanced PDF and is using the original default.

Thank you. I did this but this form looks nothing like the form on the item fulfillment print page

Any workflows or scripts running on the record? If you are using chrome, a helpful tool is NetSuite Scripted Records extension.