In order for many attachments to "activate", you must "turn on" their appropriate maneuver.
Having [Flashbulb] equipped on automaton, using [Light Maneuver] will make it use Flash when it doesn't have most enmity, or if you are in orange/red HP zone.
Using [Ice Maneuver] when in a mage build robot will "encourage it" to use more magic spells when correct attachments are equipped. More Ice = more encouragement.... to a point.
Try those.