You can send friend requests to your loved ones to stay in touch and keep them informed of all your current activities. Although it's simple to send friend requests, occasionally they won't go through. Have you ever wondered why I cannot add a friend on Facebook. Here are some reasons:
1. Your friend request has been declined by them.
2. Your friend might reach the maximum number of friends.
3. Have you recently sent a large number of friend requests.
4. Their account has been deactivated
5. They have blocked you on Facebook
6. Have you blocked them.
7. Sometimes it's a Facebook bug.