Cross check you have set the right permissions on your Task in Windows Task Scheduler. The following thread has some pictures on how to use Task Scheduler. You can use your .bat file as an argument after pointing to powershell.exe
Note that the way of using UiRobot.exe has changed. We can no longer call a .xaml file directly. The project has to be packed and then it can be called like so in community edition. The Robot has to be connected to the orchestrator if not you will get this error message