14 cadenza parking brake stuck on

So I have a 14 cadenza sxl with 36,000 miles on it. The other day I parked and turned on the parking brake, when I came back the car's rear brakes would not budge and the epb and auto hold lights were on in orange. I took the car to a Kia dealership and they said aftermarket brake pads caused this to happen (even though I never changed the brake pads). I bought the car from Carmax with only 6k miles so I doubt they changed the pads and if they did why would it act up now