I would get in touch with a real estate attorney.
If you owe the HOA past due payments, sometimes they will work with you and let you come up with a settlement amount to get back on track.
If you stop paying your mortgage, the lender will eventually foreclose on you and take the title from you/ the HOA. HOAs normally foreclose and then try to rent the property to make up for backed payments.
It really depends on what the letter says and if the HOA has already foreclosed. You can pull up foreclosure auctions on the County Clerk of Court website. If they foreclosed, you should have received notice.
But, again, I would contact an attorney and also a financial professional. You'll want to fully understand the ramifications of foreclosure before you just stop making payments. If you can pay, you may not want to take the hit to your credit and everything else.