You are seeing that message probably because you wanted to check Quiet Hours, but then one or more of the mentioned requirements isn't or aren't met yet. You may check the settings, as mentioned, or simply try restarting your phone. Beyond what has been written, it's hard to tell what has to be done, or what the user (you) wants to do - we need more information.
If your problem is about having Cortana, then needs a bit more detailed sequence of settings checks - but all of these have already been discussed elsewhere in the Internet and in these forums.
It appears that you've already created a Windows Central account after posting the same question as a guest before. I've pasted the same answer here, but your first thread would be Deleted - so all future responses to this query would be written here (avoiding clutter).