Answer: It could mean one of two things. First there may not be enough emotional reaction to the situations from the characters.
When you need to give a character a strong emotion, try to find a moment in your own past when you felt that emotion. Once I needed to find shock and horror for a character in a story. To do that I rememberd a day when I'd taken clothes in off the line, folding them into the basket as I went. When I started to put them away, a snake crawled out from between the towels and landed between me and the door. I am terified of snakes. I took all the sick, palpitating, screaming horror I felt when I saw the snake and gave those emotions to the my character. Her palms sweat, here hands shook, the room seemed to come and go. And I used what I had felt, to understand how she would feel when she walked into that horrifying situation.
Or it equally might mean the hooks need work. Hooks tie the reader's emotions to the story.
A hook should raise a question in the mind of the reader that will be answered before the story is over. Ideally they should come at in or near the transition of a scene opening and again at the close of the scene, with a "what will happen next?" hook.
Hooks heighten reader interest, pure and simple. There are teachers who will tell you that hooks are the stuff of pulp fiction and are beneath writers of literary fiction. I disagree with that. In good literary fiction, the hooks are there, but they're much more subtle. I firmly believe the difference between "page-turner commercial fiction" and " beautiful gripping literary prose," lies only in the subtlety of the hooks.
Without actually looking, I can't tell you which, but if you reread the ms with those things in mind, it may help. As a former teacher, I don't have time to read manuscripts, but I've always time for a quick question. It's always good to hear from old friends.