Oh! is it the correct foot for your machine? If so, something else is wrong. Have you tried looking on Janome site for your machine. It may show pics of this, i would hope. I have a janome MC4800 and mine fits, has a bar that moves up and down that go onto the screw.
found this pic-
http://www.janome.com/en/accessories...ven-feed-foot/
Good luck.