I guess I'm no different from anyone.
As I'm getting older, from time to time I seem to suffer from temporary memory lapses.
In this particular instance I appear to have forgotten how to use my cat door.
I know it will come back to me eventually.
So I'll stay here and think it over until it does.
(Even as a kitten I found the concept slightly bewildering. My humans had to prop the flap open with a chop-stick. Maybe I'm regressing to kittenhood and it's chop-stick time again ...)