You love your story concept but it needs something. You've been told it lacks conflict, needs more complexity, or maybe that it isn't commercial enough. Send me your synopsis and we'll work together to take it to the next level.
Story building is like constructing a house. The first step is creating a sturdy foundation. Is your premise strong enough? Is your protagonist complex and easy to relate to? Does he/she have a clear goal with ob-stacles that seem insurmountable?
You've gone through and fixed all you can. Now it's time to hand it to a professional who will tighten your sentences, eliminate redundancy, and increase the microtension. Line editing your book will help to keep your reader engaged.