Databases are picky things. They only pull up results for exactly what we put in. It may be that something as simple as a variation of the given name is holding us back. If you have entered a date of birth or date of death in the search, you may also be hindering the results. If you enter the entire date you are ruling out entries that only have January listed, not to mention any entries that may be listed with the wrong date.
Locations can be tricky too.
If you do an advanced search and enter the last known residence, you may also be eliminating the results you seek. If the field is blank, it will not be included in results for a particular state. Likewise, if only the zip code is listed, even if that zip code references an area that is in the state you are searching for, it will not pull it up in the results unless it sees the two-letter abbreviation for that state in the field. You may want to keep track of the various combinations you search for on a pad of paper. Start with just the surname and rotate the other pieces of information that you have in and out of the database.