I don’t own a 3ds but from my research let me suggest a few repairs: 1. try taking out batter and putting back in. 2. Take out ur game cards and memory to prevent damage to them. ( I damaged my ps vita memory card by not doing it) 3. Try cleaning Charging port and battery contacts. 4. Try leaving 3ds on charge overnight 5. Last resort would be to disassemble ur 3ds and check all the components with a multimeter or if u don’t have one try unplugging and repluging all modules and wires and make sure every thing is properly connected i suggest taking a picture of internals before disassembling anything. Hope it helps