To get it to bloom you may have to stress it a bit. Stop fertilzing and watering and if that doesn't do the trick, then a bit of root pruning may be necessary. Has anything else changed in the area? Is it still getting enough sun or is it completely shaded now?

Thanks Madrone - The tree sits on a bank over the sidewalk on the north side of the house. I added a sprinkler system 3 years ago, but the tree had already stopped blooming a few years prior. I did remove sod from the area around the tree and turned that area into flower beds. Because the tree stands alone and rises above the house, it seems to get plenty of sun - at least on its upper branches. Last year we had @ 6 blooms on the tree, this year none. Some years ago the tree picked up a fungus, but its been sprayed for several years now and still no blooms.