Most likely the RTC (real time clock) battery is not holding a charge anymore?
The first gen mainboards only charged the RTC battery via the charger so if you didnt plug in the laptop for some time it wouldn't boot anymore even if the main battery had charge because the laptop does not boot with a dead RTC battery
You can either replace the RTC battery yourself or framework can send an RTC battery replacement for free that uses the main battery as the RTC battery but it does require you to solder a single wire to the mainboard