If Cognos is returning blank reports, it's likely an issue from cache. You'll need to follow a few steps to fix this issue and then you'll be up and running again.
- Open the test report here (don't worry it will be blank, because you haven't fixed it yet!)
- Refresh your browser's cache.*
- Go back to your Cognos report and try again- it should work now
- If it doesn't please contact IT
Don't know how to refresh your browser's cache? No problem! Go here on Wikipedia
to find out what you need to do for your Browser and Operating System.