NHTSA Complaint #11690423 — 2015 KIA SEDONA

The car has 107,000 miles, and one day while driving, the coolant temperature suddenly spiked. I scheduled an appointment at Kia service (Glassman Kia Michigan), and the available appointment was in four weeks. The local mechanic checked the water pump and, after removing it, determined it was good, but he installed an aftermarket gasket because that's the only one available in local stores. At Kia, they replaced the pump with a new one, but the overheating problem persisted. After the car spent five weeks at the service center, they determined it was the head gasket. They offered me an engine replacement (costing $10,000). They never contacted Kia headquarters about a warranty replacement. Engines in 2015-16 Kia Sedonas have head gasket problems, and apparently, this is covered for 150,000 miles. Why do I have to pay for engine replacement?