I had that issue also. I put the carrier out with lots of catnip and treats inside.... days ahead and kept replentishing as it ran out. Then low and behold the day of, I was just able to shut the door with her in it. Good luck.
Have you tried treats and cat nip? I'm doing the same for a feral cat and seems food n treats gets her closer and closer. But I would ask a vet sometimes meds have to be given. Also Petsmart may have claming milk or so.
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