Command blocks don't work, they won't work with buttons, redstone linked up to them, lever, nothing seems to work

Command blocks won't work I have commands on, and them enabled, but they just won't work! I've tried all sorts, I've tried different accounts, I've tried different commands, I've made sure my spelling is right, I've even seen tutorials to make sure I'm doing everything right, and I am, they just don't wanna work