As I made my first vegan stew the other night (it turned out excellent, after some fixes), I realized how much writing is like cooking.
Take for example my vegan stew. I took what I knew it needed, then kind of experimented the rest of the way through.
As with writing you might have the basics, but need to let it simmer for a while. Let the story soak in what else might be needed. You read through it and realize you need more of this, that and those.
With the stew I took the first bite and went back to adding more spices. It took a while, but after ten minutes I finally got the stew I wanted.
Just as with your story, sometimes you just need to let it simmer, taste it, then figure out what you need to make it work.