OP, if you and the seller both signed a contract, the seller
is now trying to break the contract. You have three options:
(1) sue (or at least threaten to sue) to force the seller to
complete the deal as per the contract, (2) demand the seller
pay you $$$ to get out of the contract, or (3) accept the
seller's pretence that there never was a contract and forget
all about it. From what you have said, it appears the seller
hopes you will take option 3.

Una