I got a small animal carrier on Saturday. Mitzi has never been in anything other than a cage so I thought I needed to get her used to going in something. I do have a travel cage but she is always alarmed by the sight if it.
I put the animal carrier on the table where she could see it while I made a cover for it, all the time telling her how exciting this was. On Sunday I put some newspaper on top of it and put Mitzi on it so she could chew up the newspaper. Yesterday I did the same thing but also put some newspaper inside and surprisingly she let me put her in. There are slats in the sides and I was saying "peep eye" to her while she was inside. This morning when I uncovered their cage she said: "peep eye".
Definitely they can be completely unpredictable but, Jane, I think you should get some credit for doing good preparation work. It doesn't always help, but it doesn't hurt and in this case might have made the difference!