I am the seller. After the buyer home inspection and Disclosure being agreed too, I had to update the disclosure because I found a leak in the basement. Buyer is refusing to sign. What are my options?

So after the contract, after they did the home inspection and after you did the disclosure, you found a new problem, and informed them.

So since going though with the contract is most likely subject to a home inspection, and disclosure, you may have just ruined the deal, The buyer may back out, or ask for a discount to compensate for any repair cost.

You did a very MORAL thing, but I am not sure you were legally obligated to inform them of a new problem found after the disclosure and inspection. But you have, and now this gives them a reason to back out.