How long did you wait? I don't know why but sometimes it needs 10-15mins
Make sure your updated query is marked "active"... go to the device Group and expand on the left menu until you see "Dynamic Population", then expand Query and on the right side, right click and select "Reevaluate Members" Next go back up and select device group again then select "refresh"... You may have an overloaded DB and the re-evaluations are not happening as expected.
Again, my impatience does me in. It does look like it takes time to soak before the changes go into effect.
I'm good now after waiting a hour.