OpsCenter agent port setting conflict
If you have a problem with OpsCenter, check for conflicts in port settings. The OpsCenter Agent uses port 7199 by default. If you have not changed the default port, check that Cassandra or another process on the node, is not set up to use this port.
If you set the OpsCenter Agent port to a host name instead of an IP address, the DNS provider must be online to resolve the host name. If the DNS provider is not online, intermittent problems should be expected.