For about a week now one of my hubs backs up to the cloud just fine and the other hub cannot backup to the cloud. There is no error message that I can see it spins and looks like a backup is run but this shows on the backup screen:
Go to My Hubitat and Registered Hubs.
If greyed out it is probably not "online" with the cloud server. If you click Hub Details it will show you the last time it checked in.
From the hub you can also Go to Settings > Network > Network test and try to ping cloud.hubitat.com
Most common cause would be a DNS issue, either static IP set incorrectly or overly restrictive firewall / dns blocking.
I checked your hub and the "fluke" was because the hub kept disconnecting from the cloud. There is no history on frequent cloud disconnects, so it could have been a fluke on your network side.