The tree is about 5ft tall, and very healthy, but no flowers.
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