I woke up this morning to both of my C-7s reporting "Cloud connection unavailable". I only noticed because Alexa reported my lights not responding when I went to turn them on. There was no visible alert on either hub; the message only showed up when I clicked the chat-bubble in the hub UI.
(@support_team "Cloud connection unavailable" should be an alert)
I only updated to 2.3.9.174 two days ago. We'd been away 2 weeks. I think I was previously running 166.
This is the first time this has ever happened to me in 4 years. It feels like more than a coincidence that the release notes for 174 mention tweaking the cloud reconnect logic.
Rebooting both hubs restored cloud access to both of them.
And I see other people are having similar issues.