FILE TYPE DEFINITION FOR MEMOQ XLIFF

I’ve already completed the sequence “Go to Options -> Fileypes and then look on the right.  It probably says "additional filetypes exist".  Click that, select the missing one and you'll be good to go”
and XLiff Kilgray MemoQ appears in the list of File Types.  Nonetheless, when I try to open a new project and add a .mqxliff file, the file type is “unknown” for SDL Trados Studio 2014. Any idea why? Thank you.