First of all you will need to remove the battery from your phone to turn it off for about 30 seconds. Now Turn on the phone and Check.
is it not working still? Then Press Volume Up + Power button and try to Wipe data/factory reset the y7
Still not working? Then we have to Flash Stock Rom again with Fresh Files.. hold the power+ Volume up+ Volume down buttons simultaneously for 8-10 seconds until the flashing process starts automatically. When finished, stay 2min because normally first time is getting slow