Unable to move or close screen in Gnome desktop under SLES15 SP6

As a new administrator of SUSE, I am having some issues with the VNC setup under version SLES15 SP6. I have setup the system to use TigerVNC (which my client is used to) and have created the necessary files for vncserver to run ie. /etc/tigervnc/vncserver-config-defaults and I have created a specific .desktop file under /usr/share/xsessions to run my application script.

Everything runs fine and the screen looks great under the Gnome desktop, however, there is no title bar and hence no way to move or close the screens. From my various internet searches, I have determined that there is no windows manager running but how do I get this to run?

I have tried running the Exec command, within the Desktop file, with gnome-session – & gnome-terminal – prior to executing my script but neither appears to work.

However, if I start a gnome session and then run my script via a terminal window to run the application, everything works perfectly, so this suggests that the environment being created for my applications to run under is not a full gnome desktop environment.

These are my desktop and TigerVNC default entries:

[Desktop Entry]
Encoding=UTF-8
Type=Application
Exec=gnome-shell – /app/sacss/.vnc/xstartup
TryExec=/app/sacss/.vnc/xstartup
Name=SACSS
DesktopNames=SACSS
Comment=The SACSS system Environment.
#Terminal=False
#x-gnome-autostart-enabled=true

vncserver-config-defaults
session=sacss
securitytypes=vncauth,tlsvnc
geometry=2000x1200
alwaysshared

Any suggestions gratefully received…