The volume control does not go up or down when I

On volume control potentiometer carbon layer wears out with time. The easiest way would be to clean it with spirit. Turn off the unit, remove the knob, spray spirit on volume control then turn the knob back and forth around a minute, should work after. Also you can disassemble CD player and resolder pot contacts on the board, when pressure constantly applied from outside, contacts get loosen. And the best way will be to replace the pot.