Steam I Can't Set Path For Train (free Roam Sand Box)

Something's not making sense here. I've put togheter a class 20 and 2 mk1 railtour wagons on Bad Vibel to see possiblities. To get from point a to point b i need to set a path otherwise signals will be red and i can't go past them.

So the issue is 1. I sit down in the cab and i get the option to set path however if i do so the game wants me to disembark to do it. So i get up and then try but the option is grayed out now.