Hi Blake, that had to do with Meraki's growth (and the growth of the back-end systems and data centers for additional servers/shards) and the addition of the 209.206.48.0/20 address space. If you go to Help > Firewall Info you may also now see that range in the destination IP address column. In most cases, there's nothing to do, but if you're running your Meraki equipment behind restrictive firewalls that even block outbound traffic unless specifically permitted, then you would need to update those firewall rules to match that firewall info for outbound destinations. I believe the plan is to eventually remove the old/original destination IPs in favor of the 209.206 addresses, but I don't have any timeline on that, and I'd expect it to be a while.
All that said, there have been some "false positives" where I've seen that info banner in a network (my home lab network for example) where I knew it didn't apply, as I'm not blocking anything outbound, and I could safely disregard it. But it would be best to check with Meraki Support to confirm for your specific deployment, as they should have visibility into the individual firewall tests to see if they're passing or not.