I have got a rescue cat about 2 months ago and have installed a cat flap in my living room window. My cat is using the cat flap only when the flap is fully open. He is not using is head to push open the flap door unless I hold the door ajar fully with tape. When I have tried lowering the cat flap window slightly but my cat is refusing to walk through the cat flap. My cat is very timid and have tried to tempt him through with treats, but this does not really work. Today, he refused to walk though, meowed a couple of times and jumped to the middle of the living room floor before turning his back to me (cat strop!)! What can I do? Any tips?