The person who came up with the counter offer should have conditioned the acceptance of the offer on approval of the counter offer and probably a bunch of addendums,perhaps specified in the counter, which give the seller all kinds outs.I bet they did if you look for it.

If it was just in negotiation stages,the deposit wasn’t delivered, and there is any doubt as to the legal contract, which probably means escrow wasn’t opened,I might try to negotiate but not make a federal case of it.Of course that is not legal advice. Just what I would do.

I had to threaten to sue for specific performance once but the contract had been perfectly ratified, deposit had been made, and escrow instructions were signed by both parties. It cost me $267 for letter from an attorney to get things back on track.