Unfortunately, we have yet to see our first egg. They are the only birds we own, and we have spared no expense to try to make them happy. They have their own room, and our vet says that their diet is complete. There are several possible answers to your birds' problem. Most avian species require some type of courtship behavior on the part of the male for the female to ovulate.
Some species require more, others less.
The parakeets from the Australasian range are more dependent on proper courtship behavior prior to laying. The fact that they are also the groups of psittacines that have the most obvious sexual dimorphism is no coincidence. If there is a compatibility problem between the pair, you might never see eggs. Another strong possibility is that the female is laying eggs, but one or both of the birds are destroying them. Some pairs that break their eggs are not content until they have pulverized the shell to the point that you find no broken shell in the box upon gross examination.