Can you share your WmJDBC Adapter version with fix levels?
As per my knowledge, the JDBC Adapter is officially tested with a number of different SQL databases. SAG will or might support any Database that has a JDBC4 driver available with the JDBC Adapter. Check if JDBC4-compliant driver is available for Cassandra.
As a troubleshooting step add the jar file that you have for Cassandra under packages\WmJDBCAdapter\code\jars directory. Refer chap. Installing a JDBC Driver on Integration Server for more details from JDBC adapter guide.
Moreover because Cassandra is a NoSQL database, it will be recommended to use an interface (custom code) other than JDBC to interact with the database.
Kindly get in touch with SAG with a support incident to get more details and share the information with us it will be helpful.