I recently bought a house. I had a house-type in mind due to family/wfh needs (e.g., I want a 3 bed), and then a budget, which I made by seeing what those kind of houses went for locally.
So, I had a mini formula in my head. 3 beds tend to go for £300-400k, 4 beds are 400-500k. If I saw a 3 bed for £400k, I would think "that's expensive", and unless it was in a "top area", or beautifully decorated with high quality everything, i wouldn't understand why, and then i wouldn't view it. I didn't look at floor space until I was in the house and it "felt small".
I wonder if similar is happening with people who view your add? People who want a 4-bed might discount it (despite floor space) because it doesn't fit their needs (e.g. I have 2 teenagers who want their own room, and I need a home office space). And people who are looking for 3 beds just think it's too expensive for what it is, especially given that they will need to pay out a bunch of money to get it looking nice (e.g., new carpet, new bathroom etc). And then, once they've paid out that money they might be wondering whether they will get it back given that it's already "expensive" for a 3 bed house.
I think this is silly, but I also think it's "the market". I for one, hate tiny bedrooms, but I would rather have 4 small bedrooms than 3 big ones because I know a "four bedroom house" will be sold for more money, even if floor size is the same.
Added to this the slow market and high interest rates. I think if you want a quick sell, reduce it more until you start getting viewers. Or see if there is any work you can do to tart it up - can you put in new carpets, refresh the paint, re-do bathrooms and kitchen? Could you add an internal wall to one of the bedrooms to turn it into a 4-bed house? Importantly, does the agent think this would help increase the value.