Some take longer than others. Last year I brought mine out of brumation in early January and had two clutches hatching in late July. I'd say keep trying for 4 months.
Another thing I've discovered this year is that some of them won't breed with you watching. I could not get my Charcoal Ghost to breed my Bloodred female after a whole bunch of attempts. In fact, all he did was soil himself. I then left him in her cage for a couple weeks, and she started looking gravid so I took him out, and now I have eggs, presumably from him.
Just remember, you may be following the book, but they didn't read the book, so they don't always care what it says. ;-)