There must be a fourth because none of the above apply here! I was able to check that it is enabled (by calling up Cortana (Function + F9), typing “enable touchpad” and hitting “enter” as the first option was the one I was looking for); touchpad is clean; powered on/off a few times. I had noticed that the thing was lagging - total insensitivity - to the point that I was inadvertently banging my fingers on it! - for about 12 hours. I was actually in the process of going to change the sensitivity when the thing just quit working. When I hit “control” to show the location of the invisible pointer, it indicates that it is dead-center on the screen. If I use the touchpad to try to move it and hit “control” again, it has not moved. Not much of a surprise with this POS Dell (nothing but probs with this $2500 heap!), but I remain flabbergasted and on-deadline with a project that the notebook I’m typing on couldn’t begin to handle. … I am the one who would be eternally grateful!!! (In reference to the “Add your...