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
On the Desktop Sharing Preferences:
- Activate the option "Allow other users to view your desktop"
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.