Hey Tim,

Can you  repeat these steps as given below? I guess now  you are missing step no 6.

Start the Cassandra-cli connected  to your node.
Run the following:
  1. use system;
  2. set LocationInfo[utf8('L')][utf8('ClusterName')]=utf8('Brisk Cluster');
  3. exit;
  4. Run nodetool flush on this node.
  5. Update the cassandra.yaml file for the cluster_name
  6. Restart the node.

Check whether everything is fine or not. If not then delete the files in your system keyspace folder except files like Schema*.*. Every time you start cassandra node, it will compare the value between the one in system keyspace and the one in you configuration file, if they're not equal, you'll get an error. And please don't forget to keep the backup before deletion if anything goes wrong.

Hope this will help you