Ps1 script not executing properly when using Task Scheduler

As in my comment, to execute a script (*.ps1) you just need to call the -File Argument or -f for short however, doing only this, will not result in what you want (a task that is Alt-Tabbing indefinitely?) because the task would end as soon as the ObjectEvent was registered.

As a workaround, you need to find a way to keep the scheduled task alive, ergo, keep the powershell.exe process running in the background alive.

I'll list a few option so you can decide which one you like more or fits your need.

1. The easiest one, in my opinion, is just to add the -NoExit argument to your task, this will keep the task alive indefinitely, until, manually ending it / reboot / shutdown / killing the powershell.exe process / etc.

   • Program: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
   • Arguments: -WindowStyle Hidden -NoExit -f "D:\testing\script.ps1"

2. Adding a loop on the code, for this you have many options, for example
   Get-EventSubscriber | Wait-Event which, same as before, will keep the task alive indefinitely.

   • Program: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
   • Arguments: -WindowStyle Hidden -f "D:\testing\script.ps1"

   Add-Type -AssemblyName System.Windows.Forms
   
   $Timer = [System.Timers.Timer]::new(3000)
   Register-ObjectEvent -InputObject $Timer -EventName Elapsed -Action {
       [System.Windows.Forms.SendKeys]::SendWait('%{TAB}')
   }
   
   $Timer.Start()
   
   Get-EventSubscriber | Wait-Event
   

3. A loop that would keep the task alive for X days / hours / minutes:

   • Program: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
   • Arguments: -WindowStyle Hidden -f "D:\testing\script.ps1"
   • Code (you can use a [datetime] object instead of [System.Diagnostics.Stopwatch] here, your call):

   Add-Type -AssemblyName System.Windows.Forms
   
   $Timer = [System.Timers.Timer]::new(3000)
   Register-ObjectEvent -InputObject $Timer -EventName Elapsed -Action {
       [System.Windows.Forms.SendKeys]::SendWait('%{TAB}')
   }
   
   $Timer.Start()
   
   $elapsed = [System.Diagnostics.Stopwatch]::StartNew()
   
   do {
       Start-Sleep -Milliseconds 5
   }
   until($elapsed.Elapsed.Minutes -ge 60)
   
   $elapsed.Stop()
   exit 0
   

4. Last one, similar to the example before but not using an ObjectEvent at all:

   • Program: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe
   • Arguments: -WindowStyle Hidden -f "D:\testing\script.ps1"

   Add-Type -AssemblyName System.Windows.Forms
   
   $elapsed = [System.Diagnostics.Stopwatch]::StartNew()
   
   do {
       [System.Windows.Forms.SendKeys]::SendWait('%{TAB}')
       Start-Sleep -Milliseconds 3000
   }
   until($elapsed.Elapsed.Seconds -ge 30)
   
   $elapsed.Stop()
   exit 0