I started a tread already http://www.alesisdrummer.com/index.php?topic=7507.0
Tl;dr
A wire came off in the back, I soldered it back in place but nothing changed. Even tapping on the piezo sorts no effect
That's very common in e-drumming.
Eventually we all (unless we're rich or sponsored) will need to know how to replace our Piezo transducers!
Here's a video I just found but didn't have time to watch all the way through.
I did watch it far enough to see that he does explain nicely "why" we need to replace them from time to time, as well as to see him recommend where to get the replacement piezo - but that's the thing. So many e-drummers opt for a whole bag of Piezo triggers for really low price compared to a Radio Shack option, which is still pretty darned cheap.
Truly, though. We need to know how to do this. I haven't reached that stage yet, but I'm all ready to make my first order of piezo triggers and a soldering setup. I've seen a lot of people on the Alesis support forums blaming Alesis for this. Like the guy in the video says - most e-drums use these things... and they eventually just kick the bucket. It happens to them all eventually.
Hope this helps. I love my DM10 kick tower!!!
https://youtu.be/PEEBde_5_nQ