hello @M-W-Computer
I assume you did try to add the portforwarding rule on web.meraki-go.com with a webbrowser. When I did try, I selected a device from list and the screen went all green.
Then I tried this:
1. Select the VLAN the device is on and go back
2. Go to Settings - Advanced Settings - Port forwarding
3. Entering the IP manualy, first thing to do and ADD should turn to ADD
4. Enter Name, Protocol, Local and Public Port and then SAVE it
It seems web.meraki-go.com is a bit buggy lately. The android app was working fine, without any problems. You might want to use your phone to set the rules you want to apply.
Cheers