After you login successfully into the DLP console, you get a blank screen without any error.
In tomcat logs there are errors regarding Oracle database connection down, listener refused the connection, SQL exception occured, ORA-12505...
Verify if there was any Oracle or Vontu services restart before the problem shows up.
The problem is due to the start up order of the Oracle and Vontu services. This seems to be a common issue on single-tier servers where the DLP services start up before the database is fully started and available.
To prevent this problem you have to create the following dependency chain, using the instructions given in KB TECH221264. and reboot the server: