Hmm, this is interesting.
I have a C7 and a C8, they're on the same network and have worked perfectly for ages. Nothing has changed on my network. As of a few weeks ago I noticed the C7 no longer sees firmware updates. I ignored it, thinking it would iron itself out. I check yesterday and it has not, and I found this thread.
Same story as mentioned above; it's discovered by Find Hubs. All local features are working perfectly. I cannot access cloud dashboards and instead receive:
The C8 next to it continues to see updates and cloud features, operates normally, both hubs communicate with one another via Hub Mesh with no issues.
I went on to both hubs and updated the DNS settings. Previously I had 1.1.1.1, 1.0.0.1, 9.9.9.9
in the box, so cleared that out and rebooted. The C7 then found the 2.3.9.174 update, so I backed up and applied the update to both hubs. Problem solved, I thought. Nope.
The .176 update was released overnight and in that time the C7 had once again lost cloud access and can't see the update. I added the DNS entries I had before back into Network Settings, rebooted, no good. I then cleared those DNS once again, rebooted and... tada!
I'll update them both to .176 now, but if the trend continues I expect the C7 to lose its cloud access again. And to clarify, there are no other network changes happening. My router is staying the same and there are no clashing IPs. The C8 continues to operate without issue.