Voice can also be called "writing style" or writer's voice. Clive Cussler has a different "voice" than Christopher Moore. Just as Hemingway had a different voice than Joyce.
Character voice is different. That could be the way the character narrates (first person, second person...) or it could be their personality.
First person relies on character voice and personality more because the book is narrated by the MC. This form of narration confuses many people and leads to poorly written novels. I'm not certain that your novel is in first person, but it could be - which would have the opportunity to turn off a potential editor. First person is not simply telling the story using the word "I."
Here's why:
(randomly opening a very good book poorly written in first person)
I sighed, burrowed my back deeper into my bed. I was retreading the same mental ground, going over and over what I knew of demons, hoping I would somehow think of something new that would make me feel better about this.
Four "I"s in three sentences. GEEESH! Filtering much...
Here's a better example of first person (again randomly opened)
He waved a hand. "The dead are terrified of whatever is moving around out there. Necromancers can enslave them. Control them. Even destroy them."
So they can feel their power?" I asked.
"Absolutely."
"Good," I said, "I was counting on that."
Mort frowned and arched an eyebrow.
"I'm not sure how many of them are in town," I said, "I need to know where they are - or at least how many of them are here. I want you to ask the dead to help me located them."
He lifted both hands.
In the second example, the narrator isn't as front and center as the first example. There is less time spent dwelling in the MC's head and more time focused on the world(read as: story) around him.
There are more critics of the first example than the second example. Why, probably because the MC doesn't stand in the way of the story, he simply tells it. That is key. So, if your story is first person, and an editor says they don't like it, ask yourself, "Is my MC standing in the way of the story?"
Or, better (and easier) ask, "How many times am I using "I" in a paragraph?"
This is a much easier barometer of what is wrong. (Filtering)
OK, maybe you're not using first person. Maybe your MC is unlikeable or unbelievable.
We wouldn't "like" Hannibal Lector to be our narrator. We would want to root for the MC if they were were a pollyanna with no real conflict either. Or perhaps the MC is a superhero where everything comes easy. That's unbelievable in the context of a story because stories are all about conflict.
But, on the flip side of this, Norman Bates may make a believable narrator. Why? because his character is so conflicted. He wouldn't hurt a fly, right?
Without any details it would be hard to pin point what the editor didn't like.
Or perhaps you got an editor that wasn't involved in the right genre. That happens too.
So... perhaps post a bit in the Share Your Work section under the correct genre and see what folks say there. Or, pick up a few "on writing" books that deal with character development. Both would help. The first suggestion is more personalized than the second. Or simply reply back here and post some...
Amy