Power button is not jammed but can't turn on phone

The screen turns on when I charge the phone, but pressing the power button doesn't give any response. Before the battery ran out, when getting a text or call and the screen turns on, I can still use the phone even if the power button doesn't respond. But after it died and was recharged full, I need to use the power button to turn the phone on, which is impossible since it won't respond. How can I fix this?