My grapefruit tree has been in the ground 3 years and just this year produced 1 grapefruit. Fertilized (8-2-8) but have not been to successful with it.
Certified GKH Gardening Expert
There are two things that it might be. The first is that citrus trees generally need 2-6 years before they are mature enough to fruit. Your tree may not be quite mature enough to fruit.
Another possibility is that the tree may have too much nitrogen. This causes a lot of foliage to grow with little to no flowers and fruit.
The following article should be of some help to you: https://www.gardeningknowhow.com/edible/fruits/citrus/fertilizing-citrus-trees-best-practices-for-citrus-fertilizing.htm