A blank screen likely means you have an error in your PHP somewhere. To find out where it is you could enable the error logging in your cart , install the files, try to access them, and then view the log that is created. This will tell you right where the error is and you can correct it.

I suspect that during install of step 3, something was removed by accident.

The error logging is built in to your version. All you have to do is look at the log.