As a test, temporarily disable Protected Mode to see if it makes a difference.
How do I disable Protected Mode? And can I do this from say another
Open Reader and deselect: Edit > Preferences > General > Enable Protected Mode at startup
Then close Reader and try it out.
Even when I disable protected mode, I see it doesn't fill the form fields.
steve042966 , Can you try this once?
1. Go to Edit -> Preferences.
2. Uncheck 'Enable Protected mode at startup'.
Close all Reader instances.
Try opening xfdf file again and see if it fills form fields now.