Tried a few things trying to connect Samsung Galaxy Note 4. Only thing that worked was uninstalling the Samsung driver in the Device Manager of PC. Then when you connect the phone with a USB cable, there should be an auto detection and installing of the drivers. Three things are installed
Of course, your cable must be the right kind (not just a power cable) and so forth.
I got the tip by “xfaega” at: http://forum.xda-developers.com/showpost.php?p=49040275&postcount=19
Strange that this was always working then stopped. I wonder if it was that attempt to update Android recently that was continually interrupted. Darn amazing phones.