Rhododendron - still a stem with leaves at the top after 3 years!

I'm extremely new to gardening and have really only become interested since the beginning of the pandemic so I was very pleased to find this forum.

Approximately three years ago a neighbour, who has some beautiful rhododendrons in her garden, gave me a cutting, with a root attached. So I planted it in my garden, supported the stem with a cane and watered it carefully. Three years on I still have a stem with leaves at the top! It hasn't died, but neither has it grown or bushed out as I expected it to. I'd be really grateful if somebody could tell me what I'm doing wrong and how to cultivate it properly. Rhododendrons thrive in this area, but not, apparently, in my garden!

 

I had a rhododendron once which wasn't doing well. A professional gardener told me they don't like the wind so I moved mine and off it went.
They are easy to move as the root ball is shallow and contained. Being they are shallow may explain why they don't like the wind! Never thought of that until now.

 

I'd like to see a picture of the plant in question.

 

Thank you Jocko and Pete for your replies. Here is a picture.

 

It looks healthy enough, it is a bit leggy though.
Just wonder if some support might help it stand up and stop any root rock that might occur.

I'd make sure it doesn't go short of water this coming summer and maybe a top dressing of compost would help with some ericaceous fertiliser mixed in.

 

Thanks Pete. I'll follow your advice.