Since this is a classic application and not a UWP application, try using Shell Launcher v1 to launch the application as the shell to the system rather than using KIOSK mode. It is a more straight forward solution.
Shell Launcher V1: https://learn.microsoft.com/en-us/windows-hardware/customize/enterprise/shell-launcher
Here are some free utilities that work with Shell Launcher V1: https://annabooks.com/SW_SLUtility.html
There is also Shell Launcher V2, which can launch classic apps as well as UWP: https://learn.microsoft.com/en-us/windows/configuration/kiosk-shelllauncher#:~:text=Using%20Shell%20Launcher,%20you%20can%20configure%20a%20device,a%20Windows%20desktop%20application%20as%20the%20replacement%20shell.