Accessing file from FTP server works for all but one file

I have an application setup on a FTP server. When users access it, it downloads some files (also hosted on the server) needed for the install.

I have a problem with only one of those files (office.dll) a library used to interact with Microsoft Office. When the program tries to download this specific file I get this error.

"You don't have permission to access {Path}/office.dll on this server." "Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

I have checked that this file has the read and write permissions just like all the other files on the server.

Any help?