In Glasgow, Scotland, with clay soil. Moist and partial shade. For the past 2 years my rhododendron bush has not flowered, but the bush itself is flourishing. I had transplanted it to a different area of my garden, on the year before it stopped flowering.
Rhododendron Not Flowering
Certified GKH Gardening Expert
It's likely the soil. If soil has too much nitrogen, it will encourage more foliage growth as opposed to flowering, which needs more phosphorus. Use a "bloom booster" fertilizer or add some bone meal to the soil to help add some phosphorus.