This is a great example of why breeding parrots is not easy. You can do everything right and still not get results. There are many reasons why a pair might not lay eggs including the diet, infertility, age, health and the individual birds. Some birds simply are not good breeders. Greys should be 5-7 years old before you let them breed, so if your pair is younger, this may be the issue. Most likely your diet and environment are good because you have producing pairs. This pair might not like having other pairs around. A visual barrier is always recommended between breeding pairs. If they are outside, there may be something that they feel threatened by. Same if they can see out of a window. Even if old enough, the birds may just not be ready yet. All you can do is keep providing a good diet and environment and hope they start to lay. You can take them to the Vet to make sure both birds are healthy. As for your producing pairs, remember it is very important to rest your pairs in between clutches, whether the eggs hatch or not. Remove or block the nesting box and do not let them access it for at least 6 months while they rest and the hen recovers from forming and laying eggs. It takes a lot of her resources to form the eggs, and then it is physically draining for her to lay each egg. In the wild, a Grey pair would only produce once a year at the most.
Thank you for asking Lafeber,