Certified GKH Gardening Expert
It may be a pollination issue. Particularly with loquats. They can self pollinate, but do not do it well. If you add to that a lack of pollinators, the tree will not produce. I would recommend trying to hand pollinate some of the flowers with a small paintbrush the next time it flowers. If all the flowers produce, it is a general pollination issue and you will either need to hand pollinate the tree or make adjustments to attract pollinators. If only some of the flowers fruit, it is a cross pollination issue and you may want to consider planting a second tree.