currently you can only summon the scooter and the truck if you're on a street. even big free places like your farm are not considered valid summoning locations.
this is wrong and unrealistic, as long as there's no other object nearby like plants, it should be completely valid to summon vehicles on farm ground, and ify ou drive there without summoning it works. even if you build the garage on farm ground they'll be there, so please undo this restriction