If the buyer is changing his mind prior to all final signatures being on the initial contract of sale you do not have any rights to make them sign it. But be VERY thankful that they backed out now rather than down the road when you may have invested additional time off market and money in repairs to the home.
If your home was under contract and they backed out prior to signing the closing documents then you most certainly do have rights that will be outlined in your contract. If this is you circumstance contact a real estate attorney. You may be able to keep the buyer's deposit and request other damages.
It depends on your real estate transaction and the present and signed documentation. Please do not panic (because there are always remedies..) but not waste time and ask your real estate attroney for legal ways and options available to you to finalize the transaction. Good Luck.
I hope you indeed do - but each situation is different depending on your contract, signed agreements, etc. Your Realtor can help guide you, but please contact a knowledgeable real estate attorney who can specifically answer your questions as to what rights you have, if they are enforceable and reccomend the best options for you to proceed. I hope your transaction progresses smoothly.
I am sorry to hear about the challenges you're having with the buyers. I'm not certain if when you say "signing" if you're referring to closing, or merely signing the offer paperwork. Also is this a short sale where the buyers are awaiting 3rd party approval? These are answers needed to better direct you.