C6300 Router Mode Can't Be Enabled

I am having a very strange set of issues with my device. I recently bought the C6300 with the hope of simplifying my network and having a quality fast Modem Router combo. I was initially able to log on and control the router settings fine (including wifi settings and the such). As soon as the modem was set up on my Spectrum account however things got weird. I can no longer enable the router part of my device. When I log on to the settings through the web portal I now only have two buttons available (Home/Cable Connection) and only have about three buttons available in the advanced settings.  Previously I had a large number of options, and I can see them briefly when the page first loads, but then they all disappear. I have tried going into Advanced - Administration - Router Mode and turning it on, but each time the router gets back on line post-restart it defaults back to being off. Does anyone have any suggestions on how to fix this? I don't want to have to go back to my garbage Arris modem. Thanks!