We had trouble when we first got a doggie door......so we tapped up the heavy flap and tapped a towel over the open and taught them to push past the towel.....about a day later we let the flap down, but tapped over the magnets so it was easier to push thru....then within a day or two more....everyone got comfortable with the flap (feel and noise).
We currently have two new silkies in the house - one has been here before and remembered how to work the doggie door.....but the male is not sure at all...we are giving him a couple of days hoping he will follow someone out and figure it out.