NHTSA Complaint #11532344 — 2016 LINCOLN MKC

My car has had an engine light that comes on goes off throwing a code for Cylinder One Misfire since January 2023. It was 'repaired' at the dealership that I bought it from and they replaced the spark plugs and the coil and that did not stop the light from coming on and going on. I took it to another service center in my town and had it checked one of the times that the engine light was on and they used a camera and ran it through the system and found nothing wrong. It has now started to consume large amounts of coolant but I am not seeing a leak on the ground. I do not know where the coolant is going, I am now worried that it is going into the engine. I did purchase a warranty on the engine with the car but the Lincoln Dealership nearest to me will not accept the warranty because it is not a Ford/Lincoln warranty. I don't know what else to do am at a loss.