Pega Robotics works by essentially performing the same steps as a user using their applications. As such, it will not work without being logged-in to the machine (mainly due to the fact that the apps you are automating will not work when not logged-in to the machine). To run Pega Robotics Runtime, you must have a login to the machine where it will be running. The Pega RPA Service can login to the machine for you when configured with the credentials for doing so.