Cat Flap argh

[solarpoweredbarbarella]

So I fitted a cat flap yesterday, neither of my cats will go anywhere near it and one of them has lost there collar key already, never even used.
How do I get them to use it and what do I do about the key?

You could try tying the flap part up so that your cats don't have to push it to get to the outside. Once they are use to going in and out then untie the flap.
You may have to contact the company for a new collar key as I am not sure if they are sold separately.