Does the appearance of the questioner and his friend to each other on Facebook count as a meeting and seeing that fulfills the severance of relations, given that the friend does not speak to the questioner because he dislikes him, and the questioner has greeted him three times without a response from him? Is the questioner accountable for anything towards this friend?

You are not accountable for anything regarding your friend, and you have striven to connect with him. However, you must urge him to repent from the forbidden relationship that you guided him to, even if by correspondence. There is no injustice or betrayal in ending a forbidden relationship. Friendship on Facebook, along with the estrangement, is not sufficient to nullify the ruling of boycott.