Why? This was much less load on the extension cord and circuit than your use of the car charger. I wouldn't think twice about this as it's almost surely irrelevant to anything that happened later and did not damage the extension cord.My issue started when I came home from the weekend and found my roommate using the cable(14 gauge) to connect to a 12 volt jump pack on connected to his 12 volt car battery. I told him to NOT DO THAT AGAIN.
Take the charger and car to a completely different electrical service for testing. Any neighbor, any parking garage with an outlet exposed, whatever. Verify that there's some combination that will get you a green/good charge setup. Then, as best you can, change one thing at a time. Get a green with the charger directly on the outlet? Then add the extension cord. Get a green there? Then take it back to your house and try it.I then tried a different outlet, same result. I am now, today, going to turn off my by breaker and turn it back on; in case the building had a electrical issue over the weekend. If that doesn't work, I have no idea what to do.. If you have any solutions let me know.