[SOLVED] Register-ScheduledTask: The parameter is incorrect. WHICH ONE?

What am I doing here? I keep getting Register-ScheduledTask: The parameter is incorrect. I tried different combinations but same problem! I'm running PowerShell 4 on WinServer2012 and as System. This runs fine on PS7 and PS5.

        $taskname = "anyname"
        $action = New-ScheduledTaskAction -Execute $sysprepCommand -Argument $sysprepParameters
        $principal = New-ScheduledTaskPrincipal -RunLevel Highest -UserId SYSTEM
        New-ScheduledTask -Action $action -Principal $principal | Register-ScheduledTask -TaskName $taskname -Force | Start-ScheduledTask | Unregister-ScheduledTask -Confirm:$false

Solution

The parameter -Principal $principal is correct and fine. However, for 2012er Systems you need to add -LogonType ServiceAccount in case you want to use a ServiceAccount instead of a UserAccount.

Example from my environment (tested on WinSvr 2012 - 2022):

$ComputerName = $env:Computername

$Action1 = New-ScheduledTaskAction -Execute "msiexec.exe" -Argument "/I AzureConnectedMachineAgent.msi /l*v $($ComputerName)_azcmagent_update.log /qn"
$Action2 = New-ScheduledTaskAction -Execute "powershell.exe" -Argument "Disable-ScheduledTask -TaskName 'azcmagent'"
$actions = @($Action1, $Action2)

$Trigger = New-ScheduledTaskTrigger -Weekly -WeeksInterval 4 -DaysOfWeek "Saturday" -At 10AM
$taskPrincipal = New-ScheduledTaskPrincipal -UserId "NT AUTHORITY\SYSTEM" -LogonType ServiceAccount -RunLevel Highest

$ScheduledTask = New-ScheduledTask -Action $actions -Trigger $trigger -Description $TaskDescription -Principal $taskPrincipal

Register-ScheduledTask -TaskName $TaskName -InputObject $ScheduledTask