Certified GKH Gardening Expert
There can be many reasons why this is happening. Did you purchase the plants as grafted trees, or were they seedlings? Did they come from a fruit that you had eaten? If they weren't from a seed bank that knew the exact breeding of the tree then there is a chance they could be a hybrid. In this case, they may or may not fruit. If they do, then they could be completely different from the parent tree.
If these are grafted, and the genetics are known for sure then they could have too much nitrogen, and not enough phosphorus and potassium in the soil. Or the pH could be too high. Here are two articles that will give the most common reasons for citrus not producing fruit: https://www.gardeningknowhow.com/edible/fruits/lime/reasons-and-fixes-for-lime-tree-not-producing-blossoms-or-fruit.htm