Unable to access Nighthawk Admin from WWW

I have a Nighthawk WIfi Router that is sitting behind a Spectrum Arris TM1602 broadband modem.

I am able to access the browser based admin from within my lan but wish to access the admin from outside the house.  I have multiple port forwards for different devices and I can confirm I can access those services from outside (just to confirm that there is nothing magic happening with the Arris Modem blocking inbound requests.

The only controls that are obviously related about managing remotely is the "always use HTTPS to Access Router" (which I have checked).  

Attempting to access the admin I followed the very brief instructions that are embedded in the Help Center of the admin http://my.public.ip.address:8080.  I get no response.  Further I do not have any port forwarding that would clobber the 8080.