... you referred to your manuscript as a "fiction novel."
... your book was previously published by an e-book publisher and now you want a print version of it.
... the first paragraph of your cover letter had misspellings or grammatical errors.
... you sent me a boilerplate email telling me you are "seeking representation." I'm not an agent.
... you want me to publish something that you have already self-published (badly) on Amazon.
... your manuscript was 150,000 words.
... I don't like or trust your agent.
... your book has no marketing handles, no easily-told marketing story that will let me describe it in a sentence or two.
If any of the above needs explanation, you should not be submitting to agents and publishers.