Just as some humans are not attracted to each other, the same goes for animals. It's not always a given that they automatically feel attracted enough to mate, and there's little you can do about it. If the female is pecking at the male while the nest is up, keep it down and find another male for the female, or another female for the male. I think it sounds like the pair you have are not bonded and there's little you can do unfortunately.

Good luck. I raised zebra finches and I lucked out with chosing the right mate for my male and they made some beautiful chicks, but I was prepared to seperate them and find another female for my male if they did not bond. My male was a rescue. He was actually in a huge flight cage with 2 dozen other zebra finches and he was attacked so bad that his leg was bitten off. He was unsellable so I took him and he was a sweety. What beautiful songs he made! I ended up buying a white female, which I was not even 100% sure was a female until they began mating and she layed eggs. They bonded immediately.

Is it possible for you to try to get another cage set up and seperate the un-bonded pair, and try again with another bird? Or are you really bonded to the male and female pair that you have now, maybe you could return the female for another female, which your male might like better? Or vice versa? That would be my best advice.

Let us know what you decide if you can. I'd like to hear about the outcome.