I'm a first time novelist who is a month into the query process with limited success-- that is, I've gotten interest through my query letter and have sent out 4 full manuscripts and 3 partials (in addition to the 12 rejections I got from query alone).
So far I've gotten three rejections for the manuscripts that I've sent. I've also noticed that any time I'm asked to submit sample writing with my query, I always get rejected. That might not mean anything (and we're still very early in the game, really, only 20 responses total so far), but the other part of the situation is that I hired someone to help me craft my query letter. She took two drafts of mine and put them together while altering quite a bit of it. She did an amazing job but now I'm concerned that agents are liking her voice, which might be misrepresenting my voice.
Was it a mistake to have someone else write my query letter? I figured, hey, I'm a novelist, I can't write concisely. But now I'm wondering if it would have been best to put my best voice forward since that's the voice I'm ultimately trying to sell.
Yes, this was an understandable but boneheaded error. An agent is very interested in how well you write. Hiring someone else to do that writing is akin to hiring someone to woo your boyfriend and then popping in yourself for the wedding night. Surprise!
And don't give me that hooey about "I'm a novelist, I can't write concisely" Every single page of your book is made up of paragraphs. That's all a query letter is: three paragraphs.
And like anything else query writing is a LEARNED skill. There's an entire blog devoted to helping you acquire that skill.
Start over on the query. Write it yourself. Or better yet: work on your novel. You have prima facie evidence here that it's NOT working.