I keep trying to give my “expert” opinion (LOL) as someone with decades of troubleshooting and designing control systems in an industrial environment, but I am ready to give up.
Anyway, you can shotgun the solution, or proceed logically. Your choice.
4 wires gives you between 16 and 20 combinations. keep trying and you may reach the solution. ( Should have paid more attention to combinations and permutations in college).
BUT if you identify the operating coil and the relay contacts, you have only one way that hook up matters.
Operating coil terminals can be reversed, and contacts can be reversed. You already know that the contacts are hooked between the power lead supplying the starter and the solenoid terminal.
The other two wires connect to the relay coil…between the wire coming from the tractor safety circuit and the tractor frame or engine block.
how difficult is this to understand?
Without identifying what pins on the relay do what, 16 or 20 chances to get it right. (Actually more since the relay likely has more than one set of contacts, but that should not be an issue since as hooked up it did work previously ).
Take your pick.