Okay, it looks like your hardware can reach the JRiver server.
You should check that your Public IP Address is 75.167.x.x, with the complete address, of course, not edited with the x's. You can do that just by going to
http://www.whatsmyip.org/ in a browser. I expect that to be correct.
You should check that your MC Server on your LAN (Local Area Network) has an IP Address of either 192.168.0.4 or 192.168.0.2. You can check that in your router interface, or in the PCs "Network & Internet" settings.
Gizmo should check both when it tries to connect. Normally I would only expect to see one 192.168.0.x IP Address, although there may be other addresses that Windows creates for certain network functions. Or I guess your MC Server PC could have an ethernet wired connection and a wireless connection, each of which will have an IP Address.
You don't have two PCs running MC Server do you? If you have two running, maybe Gizmo is trying to connect to the wrong one? Perhaps an old PC that Gizmo can't connect to?
If all the above is correct, then can I confirm that you did try this suggestion I made?
If that doesn't work, or maybe before trying that, just delete the MC Server from Gizmo and then add it back in and test again.
In Gizmo, just press and hold on the existing listed server, and then select Delete. Then add the server back in again using your Access Key.
PS: Thanks Jim. Sigh.