These are bugs from 3 later versions, this bug causes that when you put a command block in always active and then change the syntax by changing a condition or a testfor to check that my commands are correctly written, it happens that it does not turn on, despite being in the "Always Active" condition and the only way to turn on the command block is with redstone, giving the possibility of changing the syntax but it takes up a lot of space to work with commands, in case I wanted to create short commands and avoid many chunk loaders, as in the photo, I changed the testfor from @a to @p and said command was deactivated.