Hey all, question for ya. Are you able to make an orbital strike after you take over a planet that had an opponent's factory, but had no units to defend it? The rules state that you can't make it if there was a contested area and combat. My thinking is no, but I am looking for clarification, since there wasn't a combat round performed during the Advance Order. Thanks!

You cannot. Moving your stuff into the same area as your opponent's stuff ("units or structures belonging to two factions") makes an area contested, and orbital strikes can only occur* if no areas were contested. (As the area was contested, a combat also technically occurs, though processing it is a trivial affair.)

*Barring exceptions like Corsair Raid.