My samsung GT-s6312 phone does not connect to PC. Even after connecting USB cable, My samsung GT-s6312 phone does not connect to PC. Even after connecting USB cable, please help to connect USB to PC
I know this is old, but maybe this can help someone now: 

I was using my Galaxy S5 mini as usual connecting it to my PC for common use and also as a test device for Android Studio with the developer options and USB debugging enabled and with the latest Android Studio/SDK.

So I needed to test an app in a real tablet, and when I connected the tablet (It was borrowed, and it is one from Coby brand) to the PC with android studio still running, the tablet was recognized by the PC but Android Studio did not recognized it. So after a few failed tries I disconnect the tablet and connect the S5 mini again and the problem begun: the phone started to charge but it was not recognized by the PC, nothing appeared on Windows.

I tried many options that did not work:

-Using different USB ports of the pc

-Using a different USB cable

-Reboot phone and PC

-Connecting the S5 mini in another PC

-USB debugging option checked and unchecked

-The phone has Android 4.4.2 and I was not able to see the screen with the MTP options, so I entered *#0808# and I tried every option of that menu and the connection still did not work.

-Updating android to the last release (I am not sure, maybe this helped to restore/update some configuration files, but the problems was not fixed)

Also I connected another Samsung phone with the same USB cable and the same PC and another PC and that phone is being recognized. With this I started to think something crashed in the galaxy S5, mainly because it does not appear at all in the PC, in the Device Manager nothing appeared, even there is no sign of any “!”, only charge was working, (the other phone appears with no problem) but I decided to try options in the PC side:

I installed/uninstalled Kies, (I tried using the installation of drivers by Kies). It did not work

I uninstalled/Install Android Studio/SDKs completely, and it did not work for the connection (I am not very confident of this, maybe it helped a little)
I tried to delete all drivers related in the PC with USBDeview (the procedure is better described here: http://www.topnotchtablets.com/FixUSBproblems ) and it FINALLY WORKS

So I recommend any of these options (always make a backup of everything that is important to you):

Uninstall/Install the latest Android Studio/SDKs

Update the android device to the last release

Delete all the USB drivers related to Android/Massive storage 

I hope this help anyone. So if you tried this and it still does not work, before getting my problem fixed, I was thinking about of connect the phone to MAC or Linux, and repeat some steps of before. Also restore the phone to factory state BUT I leave this as the last option.