If hard reset does not work and you have to reopen the iPad:
If you unscrew the battery and lift up with your fingernail (DO NOT USE ANYTHING METAL) or a plastic gift card it will work best. Do not bend the motherboard too much! Sometimes you do not need the plastic piece but it is the safest way to do it.
If it is not turning on afterwards and your LCD/digitizer connections are all on properly check to see if the screw is too tight on the battery connector.
*Sometimes if the screw to the battery is too tight it will hinder the iPad from turning on.*