Powerbook G4 charging light on, but no blinking battery lights. What could this be?

I have an older Powerbook G4 thatwas my aunts and uncles. They gave me the computer to help with school. I recently went to use the computer and the green charge light was on but not charging. The power cord always needed to be rotated clockwise or counter clockwise before the green light iluminated and would begin charging. This always worked for me! But now I can not get the computer to charge is dead now. I did an SMU? reset and the date warning came up, but still doesnt work for me. Sometimes when the computer is plugged in makes a hum or buzzing sound now that it will not charge. What could this be? I need my computer ASAP!