Orbi App, Login, and Parental Controls Not Working

Over the last 3 days, my Orbi system (RBK753) started acting odd.

WiFi and internet access are working fine for browsing, streaming, etc. However, the Orbi app can't connect; the web-based Orbi login page won't load; and parent controls like site filters and time limits on websites are not being enforced.

I've rebooted the Orbi and all connected devices, but nothing changed. 

I'm not connected to the guest network, if you were wondering.

Any advice?