Mike, I take it you have turned on ‘assistive touch’ where you have a virtual home button on the screen. Does the home button still make the slight click when you press it? if not give it a good clean with a cocktail stick and perhaps an alcohol wipe. Should this and the reset suggested not work consider a home button replacement but be aware that the touch id will no longer work once the original home button is replaced. It might be worth getting the new model SE, they are excellent phones.