Chargeing but wont turn on

I know its a old phone but i want to sell it, It shows the LED light at the top that is it chargeing but it woont turn on after holding the red button so i bought a battery and i let it charge for a while i shows it charge on the LCD screen somtimes but the little LED light is always red while plugged in chargeing so its chargeing but i told the power on button but it wont turn on?