Your battery may be dead and need to be replaced. Your charging port might be the issue and so you have to check the chip it's connected to.
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There are several possibilities to solving this issue.
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# Bad cable connection: There might be dirt or dust in USB cable. Also, try plugging in the charger into the wall outlet.
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# Broken charger or USB cord: Try using a different charger/cord to see if there's an issue with the current charger/cord
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# Dead battery: Try using the charger for another device. If the charger charges the other device but not yours, your battery may be dead and will need to be replaced.
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# Broken charging chip: If none of the previous suggestions are the cause, it is probably your charging port and you will need to replace the chip it is connected to.