Hi is this any help,
Open TweakUI and click "Logon" option in the left pane. Put a checkmark against the option "Show Administrator on Welcome Screen". Click OK to close TweakUI. Logoff and see if Welcome Screen lists Administrator login. Changes are immediate and you can use the Winkey + L to switch back to Welcome Screen to see Administrator account is listed.
Use this procedure to hide/unhide any user account from the Welcome Screen. Please remember, you can still login to a hidden account using CTRL+ALT+DEL classic logon method, but cannot Fast User Switch to a hidden user account