While playing a MIDI file, have the snare selected an open the articulations drop down menu (the one that says "All Articulations"). In there, you'll see what articulations the MIDI is playing.
For example - if you have a stack on "Center" articulation, but the MIDI plays the rimshot - the stack won't be played. You can then either move the MIDI notes in the Grid Editor, so they play the Center (stacked) articulation, or you can move the stacks from the center articulation to the rimshot articulation (right click on the stacks and select "Move to Stack".
For example, your Metal Confusion preset has 4 snares stacked, but when I hit the snare pad on my e drum kit only the first one plays. The other 3 do not.
Select one of the stacks and check the Velocity Gate property box - you'll see that it's set to be triggered only within a certain velocity range. That means that if you hit the Center articulation with lower velocity - the stack won't play.
If you play with more than 117 in velocity and the stack is still not playing - it means that your e-drum pad doesn't trigger the Center articulation - which has the stacked drums. Some other articulation is being triggered. Try to check that too in the articulations drop down menu (or the "MIDI mapping" property box, "MIDI monitor" property box, or the MIDI Mapping Keys view.
Post back here if you get it, or don't understand a thing what I am talking about 🙂 It's a bit tricky in the beginning to get a grip over all the aspects of the stacking system.