Have you plugged it in to charge? If so, does it show as charging? If it doesn't, try another charger cord and test your cord on another device to make sure it is working correctly. If it does show as charging, then does it start and get stuck? Or just not power on at all?
Important Note: If your device is under warranty, then I would suggest contacting the manufacturer before going past here as you don't want to do anything that could void your warranty.
In either case, I would suggest you first hold the power button down for 20-30 seconds, after charging it, and then press power again. The device should start. If it does not, but you did see it charge, then next would be to try a "Factory Reset". Note, this can cause some data loss...