When James began working on his Wolfenstein: Youngblood review, I volunteered to be his co-op buddy, but Youngblood refused to believe that he was waiting for me to join his game. "You have no friends you can join that are playing Wolfenstein: Youngblood," it told me.
That awkwardly-worded sentence frustrated me for 20 minutes, because James could see me just fine, but his invites never reached me. Eventually I figured out that to fix the problem, I had to change my Steam profile privacy settings from 'Friends Only' to 'Public.' After that, my friends list showed up in-game just fine.
I've never had that problem with a game before, and I would know if I had, because I always keep my profile set to 'Friends Only.' Bethesda is aware of the issue, so presumably it'll be fixed, although the problem isn't accurately described in its post.
According to Bethesda, "You both must also have your in-game privacy settings set to either 'Public' or 'Friends Only'" to join or invite friends. First of all, there are no 'in-game privacy settings.' And secondly, only setting my Steam profile to 'Public' fixed the issue for me. 'Friends Only' didn't work.
To change your profile privacy settings in Steam, hover over your display name in the top nav and head to your profile. Hit 'Edit Profile' in the upper right, and then select 'My Privacy Settings.'
It's annoying that I have to forego some privacy to play with a friend, but at least there's a simple solution until it's fixed.