There is a semi-detached near me that has been on the market for at least 18 months, maybe two years. The owners keep changing estate estates but never reducing the price.
There's no mystery why its not selling. Its priced the same as detached houses in the local area, and its semi-detached. A really nice detached house just up the road sold recently for 15k less than this one is on the market for. And it had two bathrooms and this only has one. And this house is a unusual design where the ground floor is a garage and utility room, which has the washing machine and dryer in, and you have to go up a flight of stairs to get to the house itself, which starts on the first floor. Which is obviously going to put some people (quite a few) off.
I don't get why the owners aren't grasping that they have just significantly overpriced. Why not just look at what other prices in their area are selling for and reach the obvious conclusion?!