a friend appearing offline

@anskiller

This might solve your problem unless it is a new issue. 

My son is on pc and I'm on xbox and we had a similar issue, but S8. It seems to have sorted itself out now though. What we had to do :

You have to set up a new club, I don't remember which of us set up the club.

If you are both in the same club, there is a button in the bottom right of the club tab that says invite all members to party. If you press that it should send an invite, even if showing offline. I don't remember if it was an admin invite or not, but try admin first.

Invite all members was the critical bit.

He appears as a friend now when he's online, but not when he's offline.

Best of luck

@anskiller you don't select him specifically, you invite all members, if this method still works. He dosn't have to show online.