Most likely the battery is about to die. Rechargeable batteries Whether nickel-metal hydride rechargeable batteries or lithium batteries, there is a maintenance problem. If the battery is not used for a long time, it must be supplemented at a certain time (about 3-4 months for nickel-metal hydride batteries, about 5-6 months for lithium batteries), if not, the battery is left there for a long time, the battery will slowly lose \"activity\" and finally completely fail. I think you have this problem with your battery. You try to fully charge the battery (the 2500mah battery supplies \"standard charge\" (slow charge) charger, which takes 25 hours), and then discharge the charge in the camera, and then recharge and discharge... So more than three times, see if the battery can be reactivated, can be good, otherwise you can only buy a new battery.
... I'll see if it works