On an iphone 6s and earlier, ipad, or ipod touch: press and hold both the home and the top (or side) buttons for at least 10 seconds, until you see the apple logo. if your device still won't turn on or start up. I went and put my ipad mini in my room and after one minute i went back in and tried to turn it on but it wouldn't turn on so i put it on charge but it would work and i have tried the power and home button so.. If you have an iphone plus, and want the home screen to rotate, go to settings > display & brightness and set display zoom to standard. if you have an ipad with a side switch, you can set the side switch to work as a rotation lock or mute switch..
My ipad ipad mini retina is out of warranty i forgot to plug in my ipad after the critical battery warning and it went some minutes following the warning. i was not worried because same thing had.