Assuming that the battery isn't empty (it can take about 15 minutes of charging before it will respond) have you tried a soft-reset/reboot to see if that gets it to boot up ? Press and hold both the sleep and home buttons for about 10 to 15 seconds, after which the Apple logo will hopefully appear and it will boot up.
iPad not turning on after a factory reset
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User profile for user: Artifactchap
Question: I did a factory reset on my iPad mini. Through iTunes it showed the restore was complete. Now the iPad will not turn on.