Registration was a pain, but I achieved it. Not sure what did it but I reinstalled with email download link (overwrote install from SharewareOnSale download) (had to kill processes with task manager). Made sure destop extender wasn’t running (checked task manager), navigated to installed apps list/GiMeSpace Desktop Extender/right click/more/run as administrator (I’m on Win 11 Pro) – this time the reg code was accepted. Don’t know why the “Registration” button is there; just opens website. The correct button is “Activate”. Not seeing the advantage of this over Windows 11 built in additional desktops but will work with it a bit.