Certified GKH Gardening Expert
This can be due to many reasons. The tree could be too young. It can take as long as 5 or 6 years before you ever see a bloom.
It could ,also, be a watering issue if you suspect the tree is of fruiting age.
Here is an article that will help: https://www.gardeningknowhow.com/edible/fruits/lemons/no-flowers-on-lemon-tree.htm