Pull out the battery, disconnect the power. Now take a close look at the centre post of the charging port in the laptop. Take a thin object and just slightly separate the centre post. This improves contact to the cord.
There should now be some more resistance to plugging in and out the cord, but it should still plug into the laptop
Do you see the power led on when you plug the laptop? if you don't then the problem may be in the power port or power supply unit in the laptop. Also in windows, what message do you get on the power icon does it say "plugged in, not charging" or "plugged in, charging" or what?