Had this exact same problem: An iPhone 6 with an aftermarket screen. After upgrade to iOS 11 the touch screen didn't work - at all. Couldn't even enter the access code. The moment for downgrade to iOS 10 has passed as Apple is no longer letting you download a signed copy of iOS 10. You can probably downgrade to iOS 10 by downloading the IPSW file from some dodgy website. But who wants do that ? Anyway, here's what worked for me: You need to do a power cycle. ... which is in fact not that easy to do. You would think that restarting the phone also did a power cycle (as is the case on a desktop computer), but this is not the case on an Apple phone. The instruction for power-down procedure is almost similar to the restart procedure, but with a twist. The instruction below is on the assumption that you cannot use the screen at all. (otherwise there are easier ways to do it). Here we go: (1) Hold down the Home button and the Power button simultaneously. Keep holding. (2) First, the screen will go black. Keep...
All of this didn't work for me. First of all : The trick about simultaneously pressing Home and Power buttons will potentially restart your iPhone 6, not reset it as many posters here says. I'm not a native English speaker but for me there's an immense difference between those two words. The word "reset" to me implies that something is lost (settings), while the word "restart" doesn't mean that. Bottom line: Don't be afraid of this procedure. You won't loose anything. Anyway: here's what worked for me: The thing is that is is not at first black screen where you need to release the two buttons immediately, it is at the second black screen. Capice? Do like this: (1) Press Home and Power buttons simultaneously and hold them (2) Screen will go black after some seconds. (continue to hold the buttons) (3) Screen will show Apple logo after some more seconds (continue to hold the buttons) (4) Screen will go black after some more seconds. Now you must immediately release those buttons. (5) The phone is now turned...