Are they hidden?
Please open the view menu, choose Setup filters command and turn off all checkboxes. (You could do it directly from the view menu, but there's no view menu shortcut for toggling the Hide matches with less than N matching tokens filter.) If the results were hidden, they would show up.
Read more about filters on Using filters page.
Maybe ask for more?
If the analysis did not take much time, try enabling the Find more matches by taking much more time option on the search page (if it's not already enabled). This will significantly improve the results on small projects.
Read more about setting optimal analysis options on Choosing analysis options page.
Windows x64 Edition?
At the time of writing, Windows x64 edition was not completely supported by Eclipse. In particular, the SimilarCode view results tree sometimes looked empty while behaving like if it was correctly filled. Many more problems were also encountered on this platform.
Please take a look at the Eclipse error log file .log located in .metadata/ subdirectory of your workspace. If any exceptions are being logged while the analysis is running (this clearly indicates a bug), they must be slowing down the process.
If you think you've encountered this case, please contact our support staff and we'll figure out how to fix that.
Is your project big enough?
If you are are testing on just a couple of files (literally), you sometimes may end up with no results because SimilarCode did not promise to find all similar fragments. Try it on a real project.
Still no luck?
Please don't hesitate to contact our support staff and tell them about your problem.