Tractor won't start with ignition switch but will when I byp it?

Hey well first I thought it was the ignition switch because when I turn the key nothing happens, so I bought one and installed it and still nothing happens. Than I thought it was the solenoid so I bought one installed it and still when you turn the key nothing happens...however when I place a screw driver across the two bolts on the solenoid it starts...any ideas what's wrong?