I recently bought a pickit2, it exhibited some very strange behaviour at first.
Mostly it appeared not to work, when plugged in it was detected some of the time and would then disappear.
I was on the point of sending it back from whence it came, when I had the idea of trying another USB cable - instant success which has continued for the past couple of weeks.
So, my pickit2 was supplied with a dud cable. I did "buzz out" the cable and the connections appeared to be correct, but it just would not work reliably.
I suggest that Smartie tries another USB cable, and if that does not work - the pickit3 is busted!
JimB