First, in order to verify that the web container is ON, try going to http://localhost:9090/denodo-restfulws/admin
You should be prompted for credentials. If you log in with a valid user (admin for example) you should see a page with the Denodo logo on the top left, and the list of tables in the admin database.
If that is the case, please check the solutions proposed for a very similar case:
In addition to that, you may find more useful information in the Tomcat logs in the folder <DENODO>/logs/apache-tomcat