Hi, all!  I'm just catching up on the posts.  We had the same type of
problem with our Advance Kits when they first arrived.  The Medela rep.
came and found the problem.  The Advance Kits had the "old" pistons,
which caused the pistons to rock, and no suction/not working.  The
Advance Kit pistons should have the word "Advance" on the white part
that houses the yellow piston.  We had to replace all the kits, and now
the Lactina's have been working.

Linda Moore, RN, IBCLC