Couch co-op and online with someone else

Hello! I might be doing something wrong. I’m currently playing couch co-op with my wife in our PS5 and we would like to invite a friend in a different country/PS5 to join our party. So far when I receive invitations or send invitations while being in couch co-op, we can’t join, but when playing solo, I can join my friend’s party without issue. Am I doing something wrong? Is it a technical limitation or a bug?

Thank you!

Forgot to mention, this is for Path of Exile 2!