my hub 3.0 has been working in modem mode for well over 2 years. Maybe even longer. This morning it decided it wouldn’t.
WiFi signal from my Asus AC3200 is strong. No internet access. Virgin hub looks ready. Rebooted hub and router. no joy. new cable between hub and router. No joy. connected laptop to modem with brand new Ethernet cable. Tried to connect to 192.168.100.1 and no joy. The hub looks to have failed in modem mode. I called 150 and they changed the setting back to router mode so I can get the wife online working from home. I have called 150 four times now. Each of them unsuccessful and extremely frustrating.
if it works in router mode there is no logical reason it will not work in modem mode - try a full reset and then go back to modem mode and see if that sorts it - if not then logic is out of the window and you need a tech to have a look or staff here to arrange a new hub