The Agent must have changed the sale method then, as he allowed three offers from Nikolina in the negotiations prior to making it a fixed price tender?
But you couldn't because the Agent allowed you several offers in negotiations but then stopped you offering again.
Why did the agent even allow a second offer from you?
It doesn't make sense to me that the Agent with 4 hot buyers would limit it to one last shot.
But the Agent may have been able to get more if he had allowed more offers ie if Nikolina topped the previous highest offer that she wasn't allowed to do.