I just got this problem a few days back and I figured it was because of a bad USB cable, so I got a new one from the Apple Store and I'm still having the issue. First off, I tested both USB ports on my Macbook with other devices and they both work fine so the USB port is not the issue. Secondly, the phone charges fine from the wall outlet so the USB cable is not the problem. I went to the Apple Support page for iPhone not appearing in iTunes and did all the steps including removing and reinstalling iTunes and the issue still happens. Worst of all, it acts like there's a "short" in the phone because sometimes when I connect it, the phone will make a noise like it is connected and then immediately after like it is not and if I wiggle the phone end of the USB cable it'll sometimes show that it is charging, however, considering I haven't had this problem with the wall charging it shouldn't be a short in the phone and sounds to be software related. And finally, if I turn the phone off and plug it in to the computer the Apple logo appears and the phone powers on, so what is going on here and what can I do to fix this? Thanks in advance.