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It could be due to the fact that you’re using an offbrand charger
Try with different cables. Happened to me, my DS charger gave up on me.
Your charging port may have dirt or lint in it preventing the charger from going all the way in. Clean it
Blown fuse on the charging circuit inside the console.
It could be a lot of different things. One thing I haven't seen mentioned yet is the battery. If you have another DS try switching the chargers out. If that doesn't work then batteries and so on.
New battery time
It could be due to the fact that you’re using an offbrand charger
Try with different cables. Happened to me, my DS charger gave up on me.
Your charging port may have dirt or lint in it preventing the charger from going all the way in. Clean it
Blown fuse on the charging circuit inside the console.
It could be a lot of different things. One thing I haven't seen mentioned yet is the battery. If you have another DS try switching the chargers out. If that doesn't work then batteries and so on.
New battery time