It's a lovely house - apart from the lack of photos, I wouldn't say there's anything inherently wrong with the images. Not perfect in some respects (random ordering of photos/little bit of clutter), but there's nothing stopping people buying there.
The living spaces, outside space and location are probably more of an issue preventing people from buying.
My house is about 15m squared smaller (3 bed), but I have a lounge, separate hallway, dining room and a kitchen that could be a kitchen diner, giving me two living spaces. Two large spaces would actually be less useful to me - especially in a 4 bed. I either wouldn't buy or would factor in building work. If you left the ad as 4 bed, but called one a bed/study, that might help, to be honest.
Outside - the garden part of the garden seems dominated by the stables. As PP have said - it either looks like not very much to a horsey person who'll want to know about land, or a non-horsey person will want to take it down. Do you ride from there? Are there hacks? Do you have a nearby field?
Location - Beautiful. But remote. It's just a waiting game to find someone who does want that. My parents' neighbours (6 miles from nearest village) took over 18 months to sell.
To do? I'd be inclined to say follow the advice above, but be prepared to wait it out a bit anyway.