2 months ago we got a 5 month old cat/kitten from a rescue. Kept it in for a couple of weeks and then unlocked the cat flap. Now every other cat I've ever had at this point as gone out like a shot and been fine.
This one has never made any attempt to go out. So I've taken her outside and stayed out with her trying to play with her, reassure her. She'll shoot straight back inside through the catflap unless I lock it. If she can't get back in then she just cowers under the guineapig hutch and refuses to move.
For the past few days I've chucked her outside every afternoon. She's currently under the hutch and not looking happy.
I'm getting fed up of emptying the cat litter tray especially as although she wees in the tray she will only poo by the side of the tray. Though the dog helps by eating the cat poo.