If you're willing to be a little unorthodox, you can try placing a thick napkin on the trackpad, closing the clamshell, turning the machine over, taking off the bottom cover, removing the battery, and then add gently pour a little alcohol onto the underside of the trackpad near where the sensitivity screw is, toward the "front" of the case (closest to where the user would be sitting). Be careful not to get the humidity sensor wet (small white dot if it hasn't been triggered... maybe red/pink/yellow if it has been triggered). The napkin absorbs the excess alcohol as it filters through the trackpad. If it was just a small spill that caused the issue, the alcohol will clear out any goo, and the click function will work again. This worked for me with two computers.