I search for days on the Prius forum for a reason why my car would not start after I had replaced the Prius battery in my car so I found out later at the end of The forum to install the orange plug in which goes on the battery and push down on the tab to make it run you can lock the breaker in by lifting up on the handle but you have to push down on the little handle. There was a very good two tutorial on how to do that on one of the posts!
That's unfortunate, because there are hundreds of posts and threads that discuss the proper installation of the HV battery safety switch, mostly due to someone working on their battery and then not being able to get the car to work.
Perhaps you can try the jump starter to start your car, and choose the appropriate jump starter according to your car model.