C# Topshelf fails to execute a powershell file

Question

After installing the service (.exe) and starting it, the powershell file in the code will be executed. There are also no error messages.

My Steps:

1. cd C:\Users\USER_XY\source\repos\ServiceApp\ServiceApp\bin\Debug\net6.0

2. .\ScriptAsService.exe install -servicename "MyService123" -displayname "My Service123" -description "This is my service123."

3. start the service (right click, start)

4. the start.txt and stop.txt will be generated but the powershell script will not be executed.

Here the c# code:

using Topshelf;

public class App
{
    static void Main(string[] args)
    {
        var exitCode = HostFactory.Run(x =>
        {
            x.Service<ScriptAsService>(s =>
            {
                s.ConstructUsing(service => new ScriptAsService());
                s.WhenStarted(service => service.Start());
                s.WhenStopped(service => service.Stop());
            });

            x.RunAsLocalSystem();
        });
    }
}


public class ScriptAsService
{
    private String _scriptfile = @"C:\Users\USER_XY\source\repos\ServiceApp\ServiceApp\bin\Debug\net6.0\myscript.ps1";

    public void Start()
    {
        File.WriteAllText("start.txt", "service started --> start scriptfile=" + _scriptfile);

        ProcessStartInfo process_start_info = new ProcessStartInfo();
        process_start_info.FileName = "powershell.exe";
        process_start_info.Arguments = this._scriptfile;
        Process process = new Process();
        process.StartInfo = process_start_info;
        process.Start();

        process.WaitForExit();
    }

    public void Stop()
    {
        File.WriteAllText("stop.txt", "service stopped");
    }
}

And here the powershell code (myscript.ps1):

$counter = 0
while (1)
{
  Add-Content info22.txt -Value "content = $counter"
  $counter++
  Start-Sleep -s 15
}

I except the info22.txt file. This file will be created by the powershell script.