Make sure the components in question are set in their menus to output Dolby Digital.
When the DN1080 receives a DD signal, it should show 5.1 on its display. That would (of course) mean the source component is sending a DD 5.1 signal.
At that point, if you don’t get DD, it simply means the program’s audio wasn’t produced with DD.
Regards,
Wayne A. Pflughaupt