If you get an “Element is missing Location String” error while trying to queue, either the Location String is blank or a new element with the same name has been created automatically in the Page File.  Usually this occurs when a user mistypes the defined element in the Feature using the wrong case.  For example, if the correct element defined is "Firstname" and the user typed "firstname" in the feature file, then "firstname" will be automatically created in the page file without a location string.