If it is showing signs of life (lights, etc.) then it is turning on, it just may not be loading. If that is the case, try starting it up in "Safe Mode" and see if it will load. If it does, while you will have limited access in that mode, it will tell you that there is something on the device that is causing the problem. Bad app, malware, virus, etc., that you will need to remove before you can use the tablet normally again. If, however, it still won't start up in "Safe Mode", then you may have to try a "Hard Reset" or worse, it could be a hardware problem.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.