Every offer on a house must be presented to the homeowner. Here in New Jersey, all offers must be presented even up to the moment of closing. A realtor cannot declare an offer too low - the realtor does not own the house. The homeowner is the only person who can decide what to accept, reject or counter.
It is both unethical and illegal in New Jersey for a listing agent to block any offer from being presented to the owner. My suggestion is that you contact your local Board of Realtors to learn what the proper procedure is in your location for presenting an offer to a homeowner.
Remember, you have the right to have your offer heard and the homeowner must be fully informed by the listing agent and no one but the owner can tell you that your offer isn't good enough. If an agent tells you that the offer is too low and refuses to present it, immediately ask for a copy of the letter from the homeowner instructing the listing agent to do so.
There is one disturbing aspect about all this - who is representing you? Don't you have an agent representing you? If so, why are you being told that your offer is too low to present?
If your own agent is telling you this, that is absolutely wrong. No matter what you want to offer, your agent is supposed to represent your interests exclusively. I am assuming that this is being done with a buyer's agent relationship. While your agent can advise you based on the homes you've been shown and market data that your offer is below where it all suggests the home will settle, your agent nonetheless must advocate fully any offer you make.
I understand that an agent can become frustrated with a buyer who offers way below where the market indicates a home will settle but that does not allow any offer to be blocked by the agent or agents involved.