Queue "queue name" failed to connect to hub "hub name"
Problem with connectivity between hubs, or remote hub is not running/not reachable.
Validate the the nimbus service is running:
ps aux | grep nimbus
or
/etc/init.d/nimbus status
Start the service if not started:
/etc/init.d/nimbus start
Validate that the hub communication is working.
Restart both hubs and check the result.