You didn't say whether you are dealing with the listing agent or with your own buyer's agent. In either case, and for whatever reason, the sellers apparently decided not to accept your offer.
Based on the information provided, it does not appear that the real estate agent did any wrongdoing. Thus, you have no complaint. Your best option at this point may simply be to move on and find another home you'd like to buy.
I don't know all the facts of your case, so obviously I don't know all the details or the timeline of what happened. I also cannot tell if you had a buyer agent on your side, or if you were dealing with a seller's agent.
I am a member of the local PASS Realtors (Plymouth Area South Shore) ... the same local board where you file a complaint. If you want to talk about it further, please give me a call or email. Just rollover my name with your mouse for the contact info.