Welcome to our community and thank you for your post. I've already located your account and have started the diagnostic process. I should have more information for you here shortly.
So it appears that the outage should have cleared already. Try performing a reset from inside the modem's user interface (http://systemcontrolcenter.com or http://192.168.0.1). Click on the grey 'i' at the top right corner of the page. Once you've reached the advanced settings, you'll see a red circle at the top of the page. Click that and a prompt will appear asking if you are sure you want to restart the modem. Click yes and allow the modem to restart.
Should that not work, please provide me with the latest state code like you did in your original post.
I would recommend calling in for live support (866-347-3292) on this issue, and provide them the state code 21.1.1. The agent should walk you through re-registering your system. If that fails, a technician may need to be dispatched to your home for a reconfiguration. It sounds as though your system may not have recovered properly from the outage.