Power button is important function for commands and needs to be working properly to do so. Is the button physically damaged or its just not responding when you press it? If its damaged then a repair shop is needed.
I'll leave a Link to register so you can communicate here as a guest account you can only post questions but can't reply
Welcome to Android Central! The main thing you can try is to swab around the Power button with rubbing alcohol, in case there's some residue in there that's causing it to be stuck. Otherwise, like mustang7757 said, bring it to a repair shop.