Unable to start Grakn session due to keyspace problem

I'm trying to reproduce the phone_calls example from the Grakn examples (client Java). Althought my keyspaces list returns a valid list of keyspaces, containing the desired phone_calls keyspace, I'm getting an INVALID_ARGUMENT: grakn.core.server.exception.TransactionException-Keyspace name is invalid: []. Keyspace name cannot start with a number, and can only contain maximum 48 characters of lower case, alphanumeric and underscore characters The server logs don't reveal any other insights... Any help is highly appreciated!

static void connectAndMigrate(Collection<Input> inputs) throws FileNotFoundException {
      
      GraknClient client = new GraknClient("localhost:48555");

      List<String> keyspacesList = new ArrayList<String>();
      keyspacesList = client.keyspaces().retrieve();
      System.out.println(client.keyspaces().retrieve());

      GraknClient.Session session = client.session(keyspacesList.get(0));

      for (Input input : inputs) {
          System.out.println("Loading from [" + input.getDataPath() + "] into Grakn ...");
          loadDataIntoGrakn(input, session);
      }

      session.close();
      client.close();
  }

A common cause for this issue is the incompatibility between the running Grakn server and the client in use. Refer to Client Java compatibility table to ensure the client you're using is compatible with the Grakn server you have running.