Usually when this happens, there's an gateway outage or a power outage of some kind. However, I checked in on the site and no one reports any issues. I remoted into the site and logged directly into the appliance - everything *looks* normal, and central management is still on.
Weirdly I had two appliances stop checking in with central right around the same time, but one restored itself after 5 minutes. The other never did. The only difference is that the appliance not checking in is on the 19 https://routerlogin.uno/, the rest are on 18 (strange DNS issues when I updated this device, I opted not to go to 19 right away on the rest of my firewalls). One is on Spectrum and the other is on Cox about 50 miles away.
Is there anything I should be looking for?