“KitKat 4.4.2 on Note 3. I can no longer transfer files between my phone and my computer. Don’t even know whether it’s a Win7 problem or an Android issue, but suspect Android since the computer does continue to recognize thumb drives and camera. I’m using the original USB cable.”
Well, sometimes the Windows can’t recognize your Android device. When you plug your phone in, it charges, but simply is not recognized as a device by Windows. The Android settings > Storage does not offer any way to check or alter MTP setting.
This could happen for many reasons, please check the following steps：
1) Please use the original USB cable
2) Make sure the drivers installed is MTP drivers rather than adb device(you do this when you unlock/root your device. This is important. thats the reason why its not getting detected.)
3) Make sure Settings ->Storage -> Menu -> USB Computer Connection is MTP.
4) USB debugging is disabled.
The Way to Enable USB Debugging
1) For Android 2.3 or earlier: Enter “Settings” > Click “Applications” > Click “Development” > Check “USB debugging”.
2) For Android 3.0 to 4.1: Enter “Settings” > Click “Developer options” > Check “USB debugging”.
3) For Android 4.2 or newer: Enter “Settings” > Click “About Phone” > Tap “Build number” for 7 times until getting a note “You are under developer mode” or “Developer mode has been enabled” > Back to “Settings” > Click “Developer options” > Check “USB debugging”.
You can read How to Enable USB Debugging on your Android Device for the details.