It will never work like that. Too much is missing and the ports are wide open. There's nothing there to direct the
steam from one end of the piston to the other while exhausting the previous cycle.
The video is with the valve case open. Just to show the slide movement and ports.
With the cover off, there is the slide and on top of that was a small springy metal strip
that looks like a tension device.
When I move the flywheel by hand, it looks like the slide is opening and closing the ports as intended.
TP
Pic with valve cover off and tension spring
Pic with cover on.