Are you saying that you change the Priority of the event to "Same as characters" the trigger works when it is touched by the character? But, when the Priority of the event is set to "Above characters", then the event does NOT trigger when it is touched?
If so, this is the correct behavior. The Priority "Above characters" would raise the event to a layer above the characters like a cloud. Even though you may be making a platform with the event "above" the characters, it is a different kind of "above"... if that makes sense.