I see the problem from that output. There are two keyspaces that are causing the problem. The keyspace testspace0 is set to have two replicas in 'datacenter1'. Also the keyspace twissandra is set to have 3 replicas in 'DC2'. The problem is that you do not have any nodes in datacenter1 or DC2.
This is a bug in OpsCenter and will be fixed in the next release, for now though this configuration will not work with OpsCenter. The workaround would be to update these keyspaces to replicate to an existing datacenter, in your case 'us-east'. Alternatively you could update the keyspaces to use SimpleStrategy which is not datacenter aware, or simply delete the keyspaces.
Regarding your question about connected nodes, that number is indicating how many agents have connected to OpsCenter, The problem may also be related to the replication bug though. Once that is resolved please see if that updates correctly and let us know.