I'm fairly new to Oracle Apex 5 and Pl/SQL.
I've watched several videos on making master detail forms and explored it in some example applications, and decided to make my own for my application as it fits the data nicely.
However, when I start my application, pull up the report, and then click the link column to edit the row, I get the error :

My guess is that the APP_ID is not transferring properly as the detail form is conditional on the APP_ID not being null and it doesn't show up.

^This is what the wizard defaulted for the link. I've tried changing it to &P1_APP_ID, which does bring me to the form, but the APP_ID is still null as the detail doesn't show up (and the form isn't pre-filled with data)