Well, not being there to actually see if you're doing anything wrong, all I can suggest is that you turn your volume up on your amp, and down on your guitar. When you get to the tapping part, turn the volume on your guitar up so that the tapping volume is just as loud as the rest of your playing. Another suggestion would be to tap harder. This may sound stupid, but seriously, I wasn't tapping loud enough at first, so I started tapping harder, and voilà, it was louder ;)