Why can my buddies and I not team up?

We are all on PS5. It should be very easy but it’s not. Normally I can click a name on my PS friends list and then “join”. I go into the game and see them but I can’t join or invite either from the social screen. We’ve all completed the intro mission. We try and load up for a game and it won’t work. Won’t work in home base. Won’t work in a mission because it autofills my team. I’m sure it’s something simple but would appreciate any help.