iPhone 8 Won't Connect To iTunes! Here's The Fix.

1. Plug your iPhone into a USB port on your Mac using a Lightning cable (also known as a charging cable).
2. In the upper left-hand corner of your Mac's screen, click on the Apple logo.
3. Click About This Mac.
4. Click System Report...
5. On the left-hand side of the menu that opens, click USB, which is the second to last option under hardware.
6. Look for iPhone in the USB device tree.

1. Quit iTunes on your Mac.
2. Disconnect all iOS devices currently connected to your Mac.
3. Open Finder on your Mac.
4. In the Finder menu at the top your Mac's screen, click Go.
5. In the Go submenu, click Go To Folder...
6. Type (or copy and paste) /private/var/db/ into the box under Go to the folder: 
7. Click Go.
8. Drag the lockdown folder into the Trash.
9. Enter your user account password to authorize the move.
10. Reconnect your iOS device to iTunes.
11. Make sure you Trust your Mac when you sync your iPhone to iTunes once again.

How To Repair Your iPhone With Apple's Mail-In Service

1. Visit Apple's support website to begin the online mail-in repair process.
2. Alternatively, call 1-800-MY-APPLE (1-800-692-7753) to set up a repair.

How To Repair Your iPhone At The Genius Bar Inside Your Local Apple Store

1. Visit Apple's website to make a Genius Bar appointment before you go into the store. Apple Stores are extremely busy, and if you don't have an appointment, you may have to wait for hours or end up being turned away. (Editor's note: I'm a former Apple tech and we're not exaggerating — please, do yourself a favor and make an appointment first!)
2. When you arrive, go to the Genius Bar to check in for your appointment.
3. Genius Bar appointments always include free diagnosis. If you're under warranty, many repairs can be done on the spot, but it all depends upon which parts are in stock. If you're not under warranty, the Genius will give you a quote for the cost of a repair.