Port forwarded webserver on Red Lion Graphite not working

I've recently upgraded from a Red Lion G306A HMI to a Red Lion Graphite G09, and have converted the program over using Crimson.
Everything works perfectly except that now I can't see the webserver (or OPC server) on the Graphite from outside the LAN - whereas with the G306 I could.

I've made sure everything is the same: ip address, port used for webserver, network settings, router settings. I've tried various Graphite models and different ip addresses and they all fail (the G306 always works).

The router is a Cisco Meraki MX60, and we have a fixed ip address.

Does anyone have a clue as to the difference between the HMI's that prevent the port forwarding of the webserver from working?

I know nothing about the Red Lion, but it would not be unusual for a manufacture to have a web-server on different ports from other models..

You could always setup a DMZ zone just to test, once you know web-server is functioning, go back and setup with correct parameters.

Just some additional information.