The file is not found on the server unless I do a case sensitive filename request. How can I make the GetFile find files in a case insensitive mode?
It entirely depends on whether the filesystem on the FTP server is case sensitive or not. Typically, on non-Windows systems, the filesystem is case-sensitive, and on Windows systems the filesystem is case-insensitive. There's nothing you can really do..
For example, on a Linux server, you might have all of these file existing simultaneously: "Abc.txt", "ABC.txt", "abC.txt", "abc.TXT", "abc.txt", etc. The FTP server can only do one thing: try to open the filename requested by the FTP client. On a case-sensitive filesystem, the match must be exact. On a case-insensitive filesystem, the FTP server will succeed in opening the file even if the case does not match.