Galaxy Note II USB connection not working
What version of Android? 

As of JellyBean 4.2.2, you'd need a newer version of ADB, as there's a security implementation built into JB 4.2.2, in that, any "unauthorised" computer with USB cable plugged in, will show the device as offline, rendering any file transfer/copying etc useless.

With the new version of ADB as downloaded from Google or for your device, you will be prompted to request authorisation and to allow it, based on a cryptographic key generated by ADB so that the computer is "trusted", then the contents can be copied/transferred.