Macbook Pro Retina – "Battery Is Not Charging" My Retina MacBook Pro is currently on 4% battery power, but when I plug it in, the battery icon up the top shows the plug icon instead of the lightning bolt icon inside it to say it's charging and stays on the same 4%. How can I fix this so that my laptop charges fully?

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This happens to me too. I clean the connectors, especially the area around the pins on the computer case. This is a very small area; last time I used a heavy paper stock card and cleaned out any dust or debris that might have been there. Problem solved!  This has happened to my computer a few times and the solution is always getting either the power connector pins clean, or the metal areas immediately adjacent cleaned. It could be a grounding issue.