Check out this post and double check the configuration of the remote system allows vnc connections:
setup Remmina for remote desktop connection
In order to be able to use Remmina, you need first to activate certain
options of the "Desktop Sharing" screen (Bash -> Desktop Sharing) on
both computers:
On the Desktop Sharing Preferences:
- Activate the option "Allow other users to view your desktop"
- Activate
the option "Allow other users to control your desktop"
Only activate the following if you are not trying to configure unattended access:
For security's sake, also:
- Activate the option "You must confirm each access to this machine"
- Activate the option "Require the user to enter this password" and
provide a password
Once the configuration is done, you can simply open
Remmina, create a new connection and specify the connection to the
other computer using VNC (virtual network computing) protocol and
using the password you used in the "Desktop Sharing" screen.
Hint: You can ignore the field "user".
Try it first without SSH and, if it works, then start playing with tunneling.