WinUI3 and Win11 Kiosk mode

Hi, I have build a program in C#/WinUi3 to use in Kiosk mode on a Windows 11 machine. The program run fine in either admin or the user to be use for Kiosk mode, but once I have set AssignedAccess to the program for the Kiosk user, when I log using that user I get something that seems like the program starting (waiting cursor and all) but a blank screen with a cursor that I can see, if I click I get a ding sound from Windows and I can Ctrl-Alt-Del to get back to the admin user.
Been trying a whole lot of things, but I can't figure out how to debug this one. Anyone with similar experience?