I can import csv into small projects but not my large project.

i created a csv of stories... before importing all of them into my big project I tried with a little test project, they came in beautifully.

then i tried in our big project, fail

tried another small project, success

tried importing via a file to our big project (instead of pasting), fail

I'm frustrated, because I need to get my work into the project we actually use. I'm stubbornly trying to get it in there (to my big project) by trying all different ways. ..but why would it work for a small project but not the project I need it to work for?