Tap to click doesn't always work and I can't find a way to increase the sensitivity on this 2011 13" MacBook Pro. It's seems worse if I haven't tapped for a few seconds and sometimes I can tap 5 times before anything happens. I was wondering if there something else to adjust before I contact Apple? I've got the updates and checked that the trackpad is clean. Most forum problems seem to be with a physical click rather than the tap function. By comparison taps on my Compaq trackpad work every time. Thanks.