Ah... You're using openplotter! That changes things.
You don't mess with the settings in OCPN but configure the external connections on openplotter.
I think you need to change the connection to openplotter (in OCPN) to in/out.
The direct connection that you have set up in OCPN won't work
I don't have a current
version of openplotter running to fiddle with. If you are running Openplotter you are better of asking for support on their support forums
... Scroll down to the bottom of the openplotter website and select support... (nope no idea why the menu is at the bottom page!).