I can't use command blocks.

When I give a command block to me, and place it on the ground, and then click it, nothing happens. It doesn't even make a sound when I place it on the ground! This is blocking many of my things that I want to do with concrete and such. I tried giving myself repeating- and chain command blocks, but they didn't work either. It's like it thinks I am in Survival Mode. I tried everything, restarting my game, computer, and I tried to go to survival and then creative mode, I tried deleting and reinstalling Minecraft, but nothing worked.