Many troubleshooting approaches to database usage focuses on the spelling of the relative's name and other details about the relative in the database.
Another approach is to look at the database itself--browse the images if possible. Does the database actually include the time period you need? Do certain dates or records appear to be missing? Does the "Frequently Asked Questions" page or "More About" page discuss how complete the records used to create the database actually are? Is the database incomplete or "in progress." These are all reasons why the person of interest may not be located in the database no matter how many ways you spell the name.
Are you using search parameters correctly? Do you know how to use wildcard operators for the site?