Error: Failed to create new Scheduled Task RemoteException: Exception calling UpdateTriggers RemoteException: You cannot call a method on a null-valued expression. RemoteException: Cannot validate argument on parameter Xml – daily task ok but monthly not

The following error displayed below is a result of a bug in the Windows Admin Center. I was able to successfully create a scheduled task on a monthly basis in my lab environment as shown below https://techdirectarchive.com/2020/03/26/how-to-create-a-scheduled-task-with-windows-admin-center/

I found this error was reported also in Windows Server user-voice
– Note: Daily tasks can be created, edited, run and deleted successfully.

This issue comes up when you select the trigger on a monthly (monthlyDOW) basis. I am sure this will be fixed soon.
– https://techcommunity.microsoft.com/t5/windows-server-insiders/scheduled-task-windows-server-2019-edit/m-p/719760
– https://windowsserver.uservoice.com/forums/295071-management-tools/suggestions/37335919–bug-not-add-new-scheduled-scheduled-tasks
– https://windowsserver.uservoice.com/forums/295047-general-feedback