Hi,
1.What is the OS version of your windows 10? Only Win 10 Enterprise or Windows 10 Education will support Shell launcher as well as some other requirements:
https://learn.microsoft.com/en-us/windows/configuration/kiosk-shelllauncher#requirements
2.There is one situation will lead to blank screen as listed below:
You cannot use the following executable as a custom shell: C:\Windows\System32\Eshell.exe. Using Eshell.exe as the default shell will result in a blank screen after user signs in.
https://learn.microsoft.com/en-us/windows-hardware/customize/enterprise/shell-launcher#enable-shell-launcher-using-control-panel
3.Also check whether the Shell Launcher version is compatible with windows Version and if necessary update has been installed.
https://learn.microsoft.com/en-us/windows/configuration/kiosk-shelllauncher#differences-between-shell-launcher-v1-and-shell-launcher-v2
Hope this helps and please help to accept as Answer if the response is useful.
Thanks,
Jenny