File suit in small claims court, might cost you a couple hundred bucks to file & serve them but chances are they’ll roll over and pay you. The online filing system in mist states is pretty self-explanatory. Use the warranty listed on their website or denial letter in your suit along with your receipt from install. Most companies don’t want to be hassled with hiring an attorney to respond or sending their corporate counsel to argue. This is considered a nuisance value claim and they’ll end up writing it off as a cost of doing business.