KIA Motors

We have a Kia Optima 2015 and are first owners. We received a recall notice in January 2019. Brought the car to the dealer ship March 2019 for check up. When we picked up the car we heard a strange noice (tick) in the engine. We brought the car back to the dealership few weeks later to have it checked.
A mechanic took the car for a ride, came back and told us nothing was wrong.
The tick sound stayed and a got worse over time.
In August we went back again to the dealership and were told if we would pay 79 dollars they would check the problem. We opted not to do this. In November the check engine light came on so we brought the car back to the dealership and after 2 weeks we were told the engine needed to be replaced.
We were asked to supply proof of maintenance which we did in November, we were then asked to proof with invoices and payment receipts the maintenance which had done to the vehicle we supplied all information in December. After asking multiple times for an update on the status we were told that we are on our own the car will not be fixed due to lack of maintenance.

So to start why did we have to supply proof of maintenance? Then had to supply all invoices and payment receipts?
What is the responsibility of Classic Kia who's mechanic ignored the sound in the engine?
What is the deal with the 10 year / 100, 000 miles warranty?

How do we get this resolved in an amicable manner?