Hi there!
First I would try the easy things first, replacing the battery and see how that goes!
Guide: [guide|1181]
If this didn't solved it, then you might want to check the connector and see if there is any dirt in it, clean it if needed.
Also check for damage, if it is damaged then it does need a replacement, but this won't be easy as soldering is required.
Please let us know how it goes!