i play a 2006 epiphone SG G400 and i dont use the neck pickup often and now it has stopped working all my volumes are up and if i change to the neck pickup it doesnt do a sound what might be the problem ?
Epiphone SG G 400
Marshall JH-1
Peavy Vyper
Marshall MG 10
Epiphone Thunderbird IV
Hartke A100
Pickups don't just die, so you've got a broken solder joint or something along those lines in your guitar. Pop open the back hatch and see if the wires from the neck pickup to the volume and pickup switch are still connected.
Hi, I'm Peter
Nice, I have the same guitar.

And I had the same problem on my bridge pickup. What I did to fix it was simply opening to all the mechanics on the back of the guitar and cleaned it without doing anything about the cables or anything. Just air-blow the whole circuit system and add some oil to it.

If it still doesn't work it can be the cables that are getting too old. Or even the pickup. After all, it's Epiphone, not Gibson.

In that case, learn how to repair it or take it to an expensive luthier. It might even be a good idea to think of upgrading your equipment.
Your guitar decided you need a killswitch.
You know, you're probably reading this saying "Hey, I'm bored, maybe this'll be funny?"
It's not. Too bad. No, I am not refunding you those 6 seconds of your life. So :P