Correction on the DFU procedure. Pulled up old instructions. Here is the instructions for iPhone 8, X, and 11 (all versions)
If all else has failed, you may need to restore your iPhone; if it won't restore normally, you'll need to put it into DFU mode.
- Plug your iPhone X or iPhone 8 into your Mac or PC.
- Make sure iTunes is running.
- Turn Off your iPhone X or iPhone 8 (if it isn't already).
- Press and hold down the On/Off button on the right side of your iPhone for 3 seconds.
- Press and hold down the volume downbutton on the left side of your iPhone while still holding down the On/Off button.
- Keep holding both buttons down for 10 seconds. (If you see the Apple logo, you've held them too long and will need to start again.)
- Let go of the On/Off Button but keep holding the volume down button for about 5 seconds. (If you see the "Plug into iTunes" screen, then you've held it too long and will need to start again.)
- If the screen stays black, that's it! Your iPhone 7should now be in DFU mode.
At this point, iTunes should show you an alert saying it's detected your iPhone 8 or iPhone and will allow it to be restored.