If he is activating the Component tool, and then is able to select a "door" from the types drop-down list in the Properties palette, then that "door" isn't a Door family at all. Because of course you have to activate the Door tool to get Doors.
So the problem is a bit confusing the way it was stated.
If he is actually activating the Door tool, but is unable to select a host wall for placement of a door, I think the possibilities revolve around the inability to select walls in the first place.
Maybe the desired wall is in a workset that isn't editable.
Maybe the desired wall is in an option set that isn't active.
Maybe the desired wall is shown only as an underlay, but the Select Underlay Elements toggle is off.
Maybe the desired wall is not actually a System Family: Wall at all, but instead something that was constructed in another way?