If someone is not appearing in your chat list, it is likely that you have blocked that person or he or she has blocked you.
To ensure you haven't blocked that person:
- Type the name of the contact you wish to check into the Search people field in the chat list.
- In the box that appears, the contact is blocked if you see the Unblock option (or, in Gmail, that the Block option is checked).
If you'd like to unblock that contact, simply click Unblock option (or uncheck the Block option in Gmail).
If you still can't see your friend in your chat list, please contact the person in question to make sure that he or she hasn't blocked you accidentally.
It is also possible that you have not yet invited this person to chat.