Execution on unattended robot


I try to understand how the UiPath.Executor works with an unattended robot. Maybe someone can explain?

The scenario I have in hand is the following:
I am connected to Windows Server 2016 as user X. The unattended robot is running on the same server under the same user credentials.
I have a powershell script doing some checks and in a specific scenario it launches a workflow.
Inside the workflow, I launch IE and another application.
When I run the powershell script manually, it works perfectly and I can see the IE and application windows.
Because i want the poweshell script to run every minute, I have setup a task in windows scheduler, again under the same user.
The schedule works, meaning that I am still connected with the same user, the powershell script is executed by the task scheduler and the workflow is triggered and running (it does the job) from inside the powershell script.

There is however on thing I do not understand:
When the execution happens from inside the task scheduler, I cannot see the IE and application windows. If fact I cannot see any UI actions the robot is executing (e.g. a message box).
Why is this happening? Is there a way to make them visible?