Auto Generate A Purchase Order

I am having a problem with some of the products in my inventory NOT populating in the Auto Generate a Purchase Order Function.

These same products ARE showing up in my Re-Order by Vendor report.

The Vendor IS set up.

The O/H inventory IS below the ROP.

There are no other PO's with the part on order.

What else can cause the inventory item to NOT appear on the Auto Generate a Purchase Order function?