Hi, everyone! I have a 2019 Ford Flex with 37,781 miles that was purchased in November 2019 with only 3 miles on it. I let my sister borrow it over the weekend to take my nephews on a summer vacation, and it ended up overheating on her 30 minutes before arriving at her destination. She said there was no other indication or behavior of the car to warn of anything wrong before the light indicator came on to show it was overheating. She immediately pulled into a Walmart lot, gave a video chat, and my teen son walked her through some basics. She purchased antifreeze, added it, checked the oil, and all seemed fine with the temperature. She drove about 10 more miles, then the car just stopped running; no warning indicators were displayed; it just stopped while she was driving on a turn-around and would no longer start. Someone pulled her to her hotel, and we drove out the following day and the car back by car trailer.

Some vehicle history: about 2 1/2 years ago, during the winter, the heater started acting up and would only heat when I accelerated. Once I'd come to a stop, it would blow the cold outside air. That following summer, the a/c went out. I had it fixed, but again, next winter, the heater would not heat unless I accelerated. I did some research and read it may be low on antifreeze, so I had my teen son add some, and that corrected the issue. Everything had been fine since then until this last weekend, when it overheated, and now it no longer wants to start up. I have uploaded a YouTube link to a video that shows what the vehicle does and the sound that occurs when we try to start it. At the end of the video, we show the dashboard. The light indicators show a check brake system, key programmed three keys total and no key detected, but the key fob is in the car, in my hand near the steering wheel. It's a push-button-to-start system; only one key fob was included when the vehicle was purchased and delivered to me. It was purchased from a Ford dealership out of state and delivered by a car carrier/freight service. I called a few times to try and get the second key fob, but with no luck. My son took a mechanic's course and received certification through our local college. He's still in high school but is able and willing to work on it if it's not too involved. He said, for example, that he would not want to work on it if it was the water pump that needed to be repaired due to how it is integrated into the motor, and he would hate to cause more issues. Any guidance or suggestions would be greatly appreciated!

https://youtube.com/shorts/J6CA4gGn4xs?si=6tY_HdCdBj_RhoJD