Hi Hitesh,
First of all, check that the document you are expecting to appear in the search results appears if you use the "normal" search. Go to the document library that you configured in the web part itself, and enter the same search term that you are trying to use in the web part. The (normal) search box is in the top right hand corner of the page (It will say "Search this site...").
You should get a bunch of results from the document library - and the search scope which shows up on the results page (just to the left of the search box that should have your query term in it) should say "This List: {Name of Library}" - that tells you that you just ran a search on just the library you are interested in.
If you get no results here, it means that either there really are no documents which match your search term in the library you are interested in (I'm assuming this is unlikely) OR it's that you are testing this on a document library that you have just set up and have only recently uploaded your "test" documents into. You need to wait until the indexing server has performed a full crawl and your documents can actually be found in the search index.
If your "normal" search returns hits for the documents that are in your library, but the web part doesn't, then the next test is to run the web part without checking any of the filters. The results should start with the line: "Results (no selections made - assuming no filtering)" - if it doesn't then you've got some of the filters selected. If *that* fails to return any hits, then I'd say we've got a bug.
Assuming that you *do* get hits when you enter the search term but no filters, then you need to check that the document(s) you expect to show up in the results have values for the columns you have selected in the web part options which match the values you have selected in the filter checkboxes. Also, begin by checking only *one* value for *one* column in testing, and make sure that the document in question really has that value set in that column.
Final two pieces of advice - firstly, documents which have blanks in the selected columns will probably never match your filter selections, because (as far as I remember) I haven't added in the option of treating a blank as a filter value (if I had, you would see "<blank>" as one of the options to choose from in the list of column values). Secondly, remember that multiple checkboxes in any one column act as though there is an OR operator between them, but that if there are several columns configured then the columns themselves act as though there is an AND between them. So if you look at the first sample screenshot on the home tab of this site, that example would look for any documents where "Document Type" was set to either "minutes" or "procedure" AND where the "Topic" was any one of "Strategy", "Remuneration", "Management" OR "Structure" (but NOT <blank>), AND it wouldn't care who the "Original Author" was, because nothing was selected in that column.
I hope this helps - let me know how you get on.
Cheers
Ron
