Re: Connecting to Cassandra from Zeppelin on EMR cluster
the 0.8.0 version of Zeppelin does not support Spark 2.4.0 yet, or better to say it is not compatible with the Scala 2.11.12 which Spark uses . Please, see more on this thread . I had the same issue  and the workaround was to downgrade the Spark version on Zeppelin and wait until the new release of Zeppelin is out.
Please, let me know in case you found a better solution.