Have you checked the charging port to make sure there is nothing in there (like dust, food, etc.)?
If that isn't the issue, I would suggest trying a new battery? They do go bad sometimes, and they don't last forever. That would be what I would check first.
Last option, the port may be damaged and need replacing. I am not sure if that model has it attached to the motherboard or not, but if it is, then the motherboard would have to be replaced. If the first two options don't work, I would suggest having a local repair person look at it.