Have you tried a full factory reset on the hub? If not then it's worth giving it a go. Press the little reset button on the back of the hub using a bent paperclip or similar, you should feel it click as you do so. Leave it pressed in for a full minute, the hub should reboot itself and restart in normal router mode as it was when first sent out.
The default login password is either on a sticker on the base of the hub or, I believe, it was 'Changeme' on the old hubs. Once back in then set it back to modem mode, let it reboot, connect your ASUS router up and then (importantly) reboot the hub again and it should see the ASUS and pass the WAN IP address across to it.
Failing that then the hub will need replacing, probably the best way is to disconnect the coax cable from it, call VM customer services and just say that the hub has failed and you have no service. They will ask you to turn it on and off again, and what colour lights are etc, just make something up. They will try to connect to the hub and fail - because there's no cable to it, conclude that it is indeed dead, and offer to send a replacement - if they have sorted out the supply chain issues a bit better then there is a good chance you will get a hub 3, not that it will make any difference to you in modem mode.
Now actually you can use your ASUS with the hub in router mode as long as you weren't using the 192.168.0.0/24 subnet for your LAN IP range. Log into the hub in router mode and disable the wifi (not essential but best to avoid clashes), connect the WAN port on your ASUS to the hub and then restart the ASUS. Your router will pick up an address of, probably, 192.168.0.10 as its WAN address with 192.168.0.1 as the gateway, ie the VM hub. Importantly, though, the ASUS will still act as a router linking that connection to your internal LAN (which is why it won't work if you are using 192.168.0.0/24 internally).
It's not ideal though, you are double natting - not generally an issue for most users, the hub will want to broadcast wifi as well, best to switch that off as mentioned above, and anything else you attach to the hub's ethernet ports or if you were to connect to the hub's wifi, then those devices will see the internet ok but not be able to communicate with anything connected to the ASUS, either wired or wireless. Which can a source of confusion and head scratching!
Like I say, not an ideal setup but perfectly workable until such time as you get a new hub if necessary, and saves having to reconfigure anything on your LAN side.
John
