everytime I had that issue it was Java related both on Server and on my machine where I was trying to access the console from. A couple of times had to wait until the server restarted to install the java update correctly. Good luck
You might wish to take a look at:
Essentially, that page shows the release notes for the FMS update to: 12.0v5
The v5 update includes the proper JAR manifest attributes so that you should not see the warning message that you currently see with your installed version of Java.
Thanks for the replies. My console is performing like it should now.
I don'e see any data now after getting Java 7/51 and v5 installed. We created a script that deletes all data then re-imports new data but the script fails.