the presser foot or what ever foot your sewing with does not feed the
fabric,, the feed dogs in the needle plate are what moves the fabric
to be sewed, the feet only hold the fabric against feed dog so the
machine can use the needle to sew the fabric.
if the fabric is not moving then the feed dogs have to be checked
can you see the feed dogs in the needle plate area are the up or
do you have a manual for the machine?
a manual help to know where the feed dog lever is, I'm sending
you a link for a manual for the machine, so you can look for the feed
dog lever, if the feed dogs are up then there is something wrong
with the feed dogs & they need to be checked.
but if the feed dogs are down then look in the manual & see where
the feed dog lever is & put it in the up position & see if that brings
the feed dogs up to the sewing position, if the feed dogs do not
come up then the feed dogs need to be checked.http://www.sewingpartsonline.com/instruction-manual-necchi-6015.aspx