Betaille is afraid of her new, raccoon-proof, automated cat door and won't come in the basement.
I think it's the whirring sound that did it. As the cat wearing the magnet approaches the door (that would be Betaille), the door raises up magically (think: a reverse guillotine) with a little whirring sound. It stays open about 20 seconds, and then comes down.
I carried Betaille up to the door, and her magnet triggered it. It whirred and opened. I tried to push her through, but she began flailing around. When I released her, she fled.
I went inside and turned off the motor, propped the door open, put a big bowl of food just inside the door, and left things that way all day. But she didn't venture in. This evening I removed the wood I'd had blocking the door and switched on the automatic features again. All was fine until I turned on the nearby clothes dryer. It triggered the new cat door, so that the door began going up and down in a 20-second cycle. Betaille sat outside in her heated box, staring at this performance with an expression of incredulity and disgust.
Fetching the cat door directions and a screwdriver, I adjusted the cat door to decrease its sensitivity to magnets and clothes dryers. It quit whirring. But now I have a vision of the raccoon down there tonight, waving a big piece of metal in front of the door...