Infertile or fertile eggs

by Deb Love

I have a pair of blue fronted amazons the hen has laid 3 eggs the first one was laid 30 days ago the second 28 and the the third 25 none of hatched even though the hen has been sat on them only leaving them for 5 minutes twice a day is there a possibility they are infertile? I thought the first egg might have hatched by now. We did see the birds mating