This was more intermittent, it seems odd to let the dns work successfully half the time for a modem that may not be authorized to be on the system. I was able to remote in just fine and stay connected.
A truly strange practice in my opinion.
That's a different description than in your first post.
Unprovisioned modem, launch a browser...gets directed to their account signup page.
Once the account signup has been done (either via the portal, or...over the phone)....the new configuration file gets uploaded to the modem...modem loads it, reboots (and now it's been provisioned). You power cycle your router to get fresh DNS, reboot computer to pick up new DNS...and you're up and running!
Modem is either provisioned, or not. No in between.
Any new modem plugged in needs to be provisioned....either via web, or...the way I do it...directly via a phone call to their support...takes less than 10 minutes. Call up. tell them you need it provisioned...they'll ask you for the MAC address of the new modem (so they can see it on their network)....they'll upload a config file, modem reboots, done.
Now, even prior to it being provisioned...yes you can still often have a device behind it talk to the internet...via IP address. Although web traffic is captured via the captive portal (http and https). And sometimes...depending on what region/nodes you're on...you can trick it by plugging in your own public DNS servers (although usually this gets blocked...if not....usually the unpermitted traffic is picked up and eventually stopped). So dunno if this was attempted...which may have lead to your being able to remote into it via LMI or other...