Make sure you use port 8080 if using http, and not the default (80) port.
If it still doesn't work then it's possible your ISP is blocking port 8080 (as it's often used by proxy servers).
To be honest however, you should probably not use http:// over the net and use https:// instead.
Asuswrt-Merlin: Customized firmware for Asus routers
Github: github.com/RMerl - Twitter: RMerlinDev
See the sticky post for more info.