After charging the battery with a CTEK trickle charger via the cigarette lighter socket, the car started fine. https://www.howacarworks.com/electrical-systems/using-a-car-battery-charger https://www.lifewire.com/why-car-battery-keeps-dying-4125506 Naturally, charging the battery back up will reverse the sulfation crystals and turn it back into electrolyte, ready to produce power again. If a battery charger does not recognize a battery, is it very likely that there is an issue with the battery, rather than the charger. I'm not going to tell you to try and utilize a battery charger to fix the issue as @MoveMoreCommentsLinkToTop has suggested in the comments, but it has been my experience when a battery has sat for an extended period of time with a constant power draw on it, the lead plates get sulfide crystallized over and will no longer take a charge. https://www.yourmechanic.com/article/how-to-charge-a-dead-car-battery Sulfation is the natural byproduct when the battery discharged. In order for the battery charger to turn on and work properly, the battery must reach at least 4 volts. If the battery is fully charged (according to the battery charger) but the voltage is 12.5 or less, the battery is sulfated. https://blog.greenflag.com/2020/how-to-charge-your-car-battery https://www.familyhandyman.com/article/battery-keeps-losing-its-charge Often times, the battery has been deeply discharged. https://mechanicbase.com/electric/how-long-to-charge-a-car-battery The battery charger does not recognize a battery. We sometimes have an issue with the driver's side sliding door not closing properly, then the battery dies. I've been charging the battery with a 12V 2 amp/10 amp charger (on 10 amp setting) for a few hours now, and it seems to be charging the battery, but I'm hearing intermittent clicking sounds coming from the area of the fuse panel next to the battery. https://www.liveabout.com/how-to-revive-a-dead-car-battery-4155742 I had my car battery tested at a couple of garages and they said the battery was fine, it was just undercharged.