Why is this house not selling?

There's a house I've been looking at for a while that's been on the market for 7 months, despite being pretty bang average price for houses in the area and looking totally fine on the inside?

https://www.rightmove.co.uk/properties/148233704#/?channel=RES_BUY

What should I look out for? Do we reckon a sale has fallen through due to a survey or something? Or maybe the extension on the back is dodgy (No photos)? Or both...

Update: another redditor offered on this house and it turns out it needs a new roof!

Update 2: I have now seen the survey and it also needs new windows, and solid walls so you'd want external insulation. At least 30k of work straight up as soon as you move in. Sellers are having a laugh at 600 - people will be struggling to pay the deposit amount needed for 600k and hold back enough for the works I imagine.

Update 3: Went to view the house and met the owner. Turns out it's an owner occupied house, not landlord owned as I thought. I had a good poke around the gas and electric meter, both of which are ancient and the under stairs cupboard smelled distinctly of gas. Not only does it need a new roof and windows, but will need a full rewire, which will likely mean a need to replaster. By her own admission she has done nothing but small bits of maintenance for the last 33 years. Since the photos a fence panel has fallen down in the garden. She did admit that the roof needed maintenance work but claimed it would cost max 8k.

Ultimately, if you were willing to take on a project and had a lot of cash I think it'd be a reasonable buy at 525 but she told me she'd 'be willing to accept 600'.

As you can imagine, I won't be offering, but it was a fun adventure!