This problem has been bugging me for ages and I can\'t seem to fix it or fully localize the source of the problem (although at times I can force it by allowing the phone to Stan
I have been in this situation a number of times and many of the above solutions usually work. Today none of them worked. Restarted ADB server, toggled USB debugging off and on, tried a different cable and port, re-installed driver, restarted computer. Experienced the same problem on other computers. No luck...
Solution for me: Restarted the android device.