Open the PRT_UI
Open the Modify Item dialog box for any of the blocks and carriers that you added.
Select the Attributes tab.
You can see that now there are no attributes.
That's because when you created the attributes before you used the prt_attributes.cfg file. So they will only appear with an item when you add it through the PRT_UI, not when you add it using code.
You have to write more code to add attributes to a particular item.