Hi, My name isXXXXX will assist you.I am sorry to hear that you are having this issue.
If you can you feel any resistance when you try and manually focus the lens there may be some trash in between the focusing ring. If there is resistance I would recommend getting it cleaned by a professional. It could save you a lot of money in the long run.Another common problem with these is that the AutoFocus motor could have failed, however it can be repaired or replaced. I have seen these get stuck and need to be jarred loose. You can hold the lens with one hand, then have a soft towel folded in the other hand and hit the lens down on the towel and see if it will come loose. I know that sounds non technical however it does work on occasion. If you cant get it working the only other options from Nikon are to clean the contacts and reattach the lens. I see that you have already tried those options.>PLEASE CLICK HERE FOR AUTHORIZED NIKON REPAIR CENTRES<