Be sure to use the ac charger and not the USB. Without a “risky” hardware mod to bridge the 5v pin on the usb port to the charging fuse, the USB charging feature doesn’t work as well as it does on modern phones meaning not at all sometimes. If you ''are'' using the ac charger and not the usb port and neither of those ports are dirty then it’s possible the charging fuse on the motherboard blew. It’s located right next to the battery connector that plugs into the motherboard and it’s very small. To replace or fix properly would require really good microsoldering skills. You can check if it’s blown with a multimeter in continuity mode. If it beeps it’s fine if not then it’s bad and needs replacing. This image shows where on the motherboard that fuse is located.
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