The battery may have been used too long and may have become seriously aged. The battery capacity has also been seriously reduced, so you will be able to run for a long time when fully charged. you need to replace the battery with a new one.
If the battery is discharged and the car cannot run, you can use a charger to charge, or you can choose to charge the battery jumper. Connect the battery levels of both vehicles with a charging cable, then rev the other vehicle so that its engine idles at high speed. Then learn how to operate your car in an exploratory way. If the battery is low, the car should start quickly, then the generator will charge the battery.
Generally, a battery will be discharged after 3 to 4 days, because lithium batteries require long-term charging. If the lithium batterym is not charged for a long time, oxygen will react, thereby volatilizing some substances. Well, that's because it has no chemistry and it can't produce electricity.