TightVncServer on Ubuntu 20.04 - Problems using MATE desktop from a VNCViewer client


I am running Ubuntu Server 20.04 on a Raspberry Pi 4. I installed TightVNCServer so I could access the MATE desktop from VNCViewer on a Windows 7 laptop. The Pi 4 is overclocked to 2Ghz and has 4GB RAM. Ubuntu is very responsive and is working fine when accessed with a keyboard/mouse attached to the Pi 4.

I start the vncserver like this:

vncserver -geometry 1920x1080 :2

However when I click on the MATE main Menu, to open it, it closes by itself after about a second so I can't use any programs. Other menus on the desktop work fine, like the shutdown "cogwheel" and the Wifi/Network menu etc..

Here is my xstartup file:


xrdb $HOME/.Xresources
xsetroot -solid grey
#x-terminal-emulator -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
x-window-manager &
# Fix to make GNOME work
mate-session &

I installed the xfce and cinnamon desktops and I don't have this problem with either of them.

Is there some thing wrong with my setup?