Q: TrackPad won't turn on after batteries were changed.

after all else fails:

take battery cap off trackpad

delete trackpad in preferences

turn off bluetooth

replace battery cap

turn on bluetooth

turn on trackpad

add trackpad back in preferences

reconnect

worked for me after nothing else would

I have the same problem. I can't turn it on anymore and it is only been used on my desk.

I contacted Apple Care Support and said that i don't was the only person with this problem as you can see on this thread for example. He said that they have not recieved enough complaints to call some off the products back. He would not give me a new because it is 2 years and just 2 months old. I dont think this can be okay, when you buy so expensive stuff from the company Apple.

So folks!! Contact Apple Care Support and tell about your problem. Maybe we all can get new when they know about everybody with the problem, like the iPhone 5 battery or the chargers.

Had the same problem.

8 months old trackpad, used by regularly basis, wouldnt suddently turn on any longer...

Tried various kinds of working batteries, popped the spring with chopstick, hit it (softly) different places and stuffed it with aluminium foils. Nothing worked...

Tooked a break, made some coffee and tried all the above solutions one more time - this with succes. It was the foil-trick which did the magic.

So, if you dont have succes 1., 2., or 3. third, then just keep on trying

Thanks for your solutions!!

I was having the same problem, and after much trial and error (cleaning the points, bouncing the spring, etc.), I discovered that the problem in my case was simply that the power button was a little wonky: rather than press straight down on it, I have to press it along the top edge (when the trackpad is lying flat). Pressing it anywhere else will not turn it on. I have changed batteries and replicated the result. That's just my case, but if you still haven't solved your problem, give that a try.

Give this a try.  Many years ago my HP calculator would not work.  An HP tech gave me some counter-intuitive advice.  1. Remove the batteries 2. Reverse the polarity of the batteries. (You heard right. In the Mac mouse place the positive + end on both the batteries at the bottom in the slot.) 3. Turn the unit on. 4. After about a minute take out the batteries and put them back in the correct way.

I tried this with my misbehaving Mac Mouse, and it worked like a charm.  Don't ask me why.  But that HP tech's advice still holds true.

Good luck.

I had this issue.  Turns out that the track pad was also paired with another computer in my house.  I needed to get that computer to forget the device and then it worked fine with my MBP.

This happens every time the batteries get changed and it is dumb!

DO NOT go to trackpad in SETTINGS.

GO TO "Bluetooth, click bluetooth "off" then "on" and highlight the darn thing which will not pair and hey presto it does!

I kept forgetting this but have made a Stickie...

After all else had failed, I tried this suggestion, with incredulity mind you; but it worked.

Apple, take heed, there is something that is wrong with the firmware on these units. Mine is a A1339.  The batteries were out for about 10 months.  Tried three pairs of fresh batteries, nothing, it would not turn on (so pairing was not the issue here).  But reversing the polarity, holding power for 3 seconds, returning the batteries to their "correct" polarity and a push of the button later, we had a green "on" light.

So, BishopBullwinkle... thank you, saved me 80 bucks. 

very  helpful, worked for me too, many thanks