If your account is blocked from sending someone a friend request, it may be because friend requests you’ve sent have gone unanswered or been marked as unwelcome. In the future, you should send friend requests to people you have a real-life connection to, like your friends, family, coworkers or classmates. Make sure to use your authentic name and picture to help the people you're friending recognize you.
If you're interested in receiving updates from people you find interesting, but don't know personally (ex: journalists, celebrities, political figures), try following them instead of sending them friend requests.