How to configure a Gateway in Bridge mode. Can no longer do it via webpage and no option in App.

My Gateway is in bridge mode. I used to be able to administer it via http://10.0.0.1 but I can no longer do that. I cannot do it via the app either. How can I now configure my gateway? 

The xFinity Assistant was, unfortunately, completely useless and gave a non-sensical answer to the question above. I asked to be transferred to an agent, but no luck.

If I go to http://10.0.0.1 I get the message to use the app instead. But when I log in to the app and go to the WiFi tab, there is no option to configure the Gateway either. And I cannot turn on admin tool access (as Support articles mention), since um, there is no option to do so. So I am now stuck in an infinite loop.