Co-op Campaign

Ford some reason when I send my brother an invite for company op campaign he doesn’t get it and can’t join me, can anyone help?

Are you on PC or Xbox?

Are you both in the same house on the same connection?

Do you have open NAT settings?

If you are on PC. try via Xbox app instead. Works every time for me. Click his name then join his game.
Another possible way is if you bring up Pause-menu and on the frontpage (Home) you might have an option to ‘Join’ your friend. Not always there for some reason.
If neither works, try creating a session first.