Dear Customer, I am very sorry to learn of this unfortunate situation.
Unfortunately, an HOA has a right to require repairs in this manner (I assume that the HOA is acting within the scope of its authority under your CC&Rs (or governing documents), if it is not (i.e. it is claiming it has authority to force repairs or upkeep but there is no actual written authority to do so in the governing documents, then you can defend their enforcement action on this basis).
A homeowner's financial ability to pay for repairs is not a basis to object to enforcement.
You did note that you have tried to negotiate for more time to perform repairs, but you also stated that you have a concrete plan to perform these repairs in the upcoming future. It may be worth trying a formal mediation with the Board to try to get additional time. A third party neutral may be able to get you additional time in exchange for some assurance that the work will actually be done (you may face a fine or penalty, but hopefully this will be done in a way that you can actually do the repairs - ultimately this should be the goal of the HOA, getting the repairs done to the home without forcing the home to go into foreclosure or short sale (which isn't going to help anyone)).
If you wish to pursue mediation, contact your local (city or county) bar association and ask for referrals to local mediators with experience in HOA matters. Then contact the mediator(s), once you select one you feel comfortable with, ask them to set up a mediation with the Board - they will take care of contacting the HOA board and set up a mediation for you. Hopefully you can reach a "mutually agreeable resolution" that will meet both your financial needs, and the HOA's interest in maintaining the appearance and structural concerns of the Association.