Have you tried writing the ending and then working back? Sometimes it helps to know where you want the thing to end up.
Have you had a ‘chat’ with the characters? Sometimes you have to listen to them, to see what their problem is.
If it’s not working, perhaps there is a different story trying to get written and your original idea is getting in the way.
If all else fails I find coffee and chocolate helps. (Not with the writing, but definitely with the feeling.)