Why does my rhododendron not flower?
I have had two rhododendrons that are about four years old. Neither flowers. What can I do to change this?
This article gives you the basics of rhodedendron care: https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/rhododendron-care.htm
After you've checked on the basic requirements to see if there are problems there, there are a couple of other possibilities. The first is that you're pruning at the wrong time (any time after late spring) and cutting off the flower buds. Here's an article on pruning: https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/pruning-rhododendrons.htm
The second is that deer may be eating the flower buds, which they are fond of. Here's an article about protecting from deer: https://www.gardeningknowhow.com/plant-problems/pests/deer/deer-repellents.htm