Q.How To Encourage Fruit Growth On Lemon Tree?
It bloomed and produced for 2 years, Since then foliage only!

Certified GKH Gardening Expert
If this isn't fertilized with a citrus specific fertilizer a few times per year, then it is lacking in food.
I would make sure to feed the tree properly to ensure a good fruit set.
Here are some articles that will help:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-not-fruiting.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/learn-about-fertilizer-for-a-lemon-tree.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/how-to-grow-a-lemon-tree.htm