I had the exact same thing happen, just with a 2014 Hyundai. Only aftermarket remote starts were available when I bought the car, so that's what was installed at the dealer. Took it in for a recall repair 3 years later and the remote start was broken when I picked the car up.
Contacted multiple dealerships and they wouldn't touch it since it's aftermarket (despite being installed at a dealer). The shop that did the recall repair flat out said I couldn't prove it was their work that broke it so they're not responsible. My only option was to take it to a local shop that does that type of work. Audio install and aftermarket mod shops were the best bet.