I get 'refused by the computer' message when connecting to VNC server.. (ubuntu-22.04.)

Tdoay, I received a new ubuntu 22.04 machine.
After setting the static IP network, I followed https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-vnc-on-ubuntu-22-04 to setup vncserver and when I typed in (etri is the account name)

ssh -L 5900:localhost:5901 -C -N -l etri 129.254.32.172

it hung up. So I waited a minute and pressed ctrl-C. (why are there so many tutorials not working for me.. I have set-up vnc server many times and I use it everyday)
I called the person who delivered this machine and he says he already checked he has seen vnc connection working already. (I should have asked him earlier. so I was doing unnecessary thing..)

When I start vncserver, I get this responsed.

etri@etri:~$ vncserver :2

New Xtigervnc server 'etri:2 (etri)' on port 5902 for display :2.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /home/etri/.vnc/passwd :2 to connect to the VNC server.


=================== tail /home/etri/.vnc/etri:5902.log ===================
/usr/bin/startxfce4: X server already running on display :2
xfce4-session: Another session manager is already running
==========================================================================

Session startup via '/home/etri/.vnc/xstartup' exited with status 1!

Maybe try something simple first, e.g.,
    tigervncserver -xstartup /usr/bin/xterm
The X session exited with status 1!
Killing Xtigervnc process ID 3404... success!

And this is the .vnc/xstartup code.

#!/bin/bash
xrdb $HOME/.Xresources
exec startxfce4

I'm afraied the ssl -L ... command has made something wrong... Can anyone tell me what is wrong? (I created .Xresources by touch .Xresources earlier).

I recevied a phone call from the person who delivered the machine.
The correct method to make it work is :
You change the ./vnc/xstartup to its original below.

#!/bin/sh
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
exec startxfce4

And then start the vnc server using this command. (when the display is :2)

vncserver -localhost no -geometry 7680x2160 :2

And the vnc works just fine.
(I had tried -localhost no option and the SESSION_MANAGER, DBUS_SESSION_BUS_ADDRESS stuff, but I don't know why they are used sometimes and why the shouldn't... But hope this will help someone later.)