I'm trying to fix my brother's phone. The screen is completely unresponsive. I tried swiping around to try getting the passcode wrong to see if it would vibrate to no avail. The phone's lock button is broken, so I can't restart it that way, and it was never used with a computer, so when I tried to plug it in and fix it that way, iTunes asks me to confirm that I want to allow this device access by clicking something on the phone (which obviously I cannot do). I read somewhere that the LCD connector may be loose. Could this be the problem? Is there any way to fix this? Thank you!
It sounds a lot like that to me. You could disconnect and reconnect the LCD cable yourself, if you are comfortable with opening up the iPhone. You would need a special iPhone screwdriver (one with 5-point star tip, AKA pentalobe), which can really only be found online.
You could also take it in to a repair shop, if any are around you, but whatever you choose don't over pay, as a working iPhone 4s is only worth around $100.