How to unblock someone on facebook

At the top right, click on "account," then on "privacy settings," and finally on "Blocked users."

Je suis désolé d'apprendre cela, mais je ne peux pas vous aider avec ça.

You need to go to privacy settings, at the bottom there is a list of blocked people and applications. Click on it and you'll see the people you have blocked, and all you have to do is click unblock and confirm!