Bot is not triggered from Windows task scheduler once Uipath was upgraded to 2018. Seems Windows scheduler is not supported from since 2017. But is there any other way to schedule the process without using an Orchestrator?.
Task scheduler is no longer officially supported by Uipath, but i believe it should still work. Check if you are pointing the correct robot.exe path under scheduled task.
You can try creating a batch file,with the below content:
start "" /min "C:\Users\user_name\AppData\Local\UiPath\app-18.2.2\UiRobot.exe" /file:"path_of_xaml_file"
Created just yesterday first scheduled task with Task Schduler following these instructions: