I tried to sync my iPhone with my iTunes, but it keeps saying "This iPhone cannot be synced because it cannot be found." Help please?

Can someone tell me what to do about this? I hate iTunes enough and now this. This problem has never happened before, but I've always had issues with music being taken off my phone, tracks being duplicated, tracks being deleted permanently, etc. So if anyone has an answer to any of these problems, it would be very much appreciated.