You can receive this message for a couple of reasons. The first one being if you are not sending friend requests in the “Member with Things in Common” section you may receive this message because of Facebook’s protocols. Facebook will deny the request whether you are using automation or trying it manually, if you do not send friend requests in the “Member with Things in Common” section. If you have already sent a lot of requests to new members or members you don't have things in common with then give it a good 24 hours for FB to reset and you can start sending friend requests in the Member with things in common section.
The second reason could be that Facebook user has a setting on their account that prevents them from receiving friend requests from anyone.