Arris SBG6900-AC web manager

Solution found!

Like many people on this thread, I lost access to my Arris SBG6900-AC web manager. I tried dozens of suggestions throughout the blogs, tech supports, web videos, Chrome, Edge, Foxfire, Duckduckgo, and factory resetting the device, all without success.

I finally installed the outdated Internet explorer 11 on my Windows 10 laptop and behold, it works! Works via both Ethernet and WiFi. You'll need to click through the error messages and accept the unsafe web access warning within the "more information" link.

Try the Explorer 11 route before unnecessarily factory resetting the device. I hope this works for you too.