I noticed my hub mesh quit working. Looking in the hubs, one of them shows a 169.x.x.x auto config address for the remote hub. But both of my hubs have the correct IP as they always have.
Both hubs are on UPS's, but I suspect this may have happened over the weekend when I rebooted my firewall for a memory upgrade.
I just rebooted both hubs, now my hub mesh link is totally missing!
[EDIT] After waiting a few more minutes after reboots, the hub mesh link showed back up and seems to be working.