No Add Friend Button but many mutual friends?

Question

An old friend and I have 18 mutual Facebook friends. Until a month ago, I could have sent him a friend request, as the button to add friend was there.

Then all of a sudden, the "add friend" button is gone, although there is still a button to send message. I am not blocked from his page, I just can't add as a friend.

How is it possible that the Add Friend option has mysteriously disappeared when we have so many mutual friends on Facebook and the only privacy settings for "who can send you friend requests" are "everyone" and "friends of friends"?

I should add: 3 months ago I sent him a friend request, which he declined at the time, but after that the "add friend" button was still there. I never sent another request. The add friend button has been there all along until, like I said, it just strangely disappeared like literally overnight!

Answer 1

When you refuse to accept a friend request you could check an option to block all future friend request from that person. (Its not the same as blocking that person completely.)

Answer 2

The button can appear/disappear based on previous actions, for example, a denied request or blocking then unblocking a user.

Your friend should still be able to send a request to you, if not, submit a help request to facebook.com/help. You can also try using m.facebook.com or a Facebook mobile application.

(I have tested this scenario before and seen this behaviour already)