One item that seems to apply overall is the need to RESET before leaving session edit. Located at bottom of the page. On my system the session can be started, driver and train assigned but no instructions are passed. They are normally seen on the info stripe at the bottom to the right. Even in "normal" operation I sometimes have to do this reset after an edit.
I have it working now but still not sure if there is a secret to what is in the fields. Driver assignment may be one of those. I can now bring up the schedule for the current setup showing arrival and departure times when in driver mode (Windows Menu). Also, the target consists location may be something but not sure. I moved mine to a different siding and that was one cause.