I've had my TP Link router with parent controls for about a year.  When I first got it set up and started using the Tether app, I was able to do thing from offsite, like, for example, turn off kids wifi/Intenet access from work.  Now, however, if my phone is not on the same LAN as the router, the Tether app fails to find the router on the first screen. 

Any ideas what is going on?  I assumed that once the router was associated with the app, and the app would have some kind of back-door way into the router even when the android devices is not directly connected to the router.  Note that this router is directly behind my cable modem, but also I haven't set up and special rules / ports in the firewall that might let the app talk to it directly from the Internet.