Fatah agreed to start negotiating a 2 state solution 25 years ago, at which point they immediately started losing support. Israel were unlikely ever to go along with it. It was always a poor solution - the Palestinian majority would be forced onto smaller, poorer, land than the jewish minority. Now, the jewish settlers have spread over such a wide area, there is no meaningful land that could be given to Palestine without kicking the settlers off. And Israel will never kick those settlers off.
They also cant support a single, secular, state, with full right of return for all 9 million Palestinians, because then they'd be a minority in 'their own' land