Why does home button not work on new screen?

Could be an issue with the New Screen, if the cables are damaged of faulty then the home button just completely stops working even if everything else on the device is fine (found this out the hard way when removing a screen to do a new rear camera). Unfortunately you can't test this by trying a different home button to see if that also fails on that screen(which would be fairly cheap) because only the original button works in any capacity on the 7's so you'll probably need another screen to test.