Have you pruned it? Generally, a light pruning each year in late winter/early spring will help keep the tree looking and performing at its best. Be sure to remove any diseased/broken branches as well as any sucker growth at the base of the tree. Also, does the tree get enough light? For these trees to bloom successfully, they require full sun.
Since they normally prefer somewhat sandy soil, this could also be a factor as far as flowering goes, as the soil may be lacking phosphorus (a soil test would determine this). If this is the case, adding some high phosphorus fertilizer, like bone meal, to the soil around your tree should help encourage blooming. In fact, phosphorus is responsible for flowering in plants and this is one of the most common reasons for non-blooming issues. Here is more information on that: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm