Hi-
There might be a lot of factors involved, just a matter of ruling them out one at a time. I am not sure if you are trying to do this on a domestic sewing machine, but I know on my Babylock QCP when I switch the hopping foot and what to do FMQ the first thing I have to do is drop the feed dogs (or you can cover them with tape) and set my presser foot to zero..meaning there is not a lot of pressure from the foot. Have you done those initial things yet?