For at least a year now or even longer, I also encounter the matchmkaing issues when playing with friends: In a friend’s custom game, one cannot enter (with the “door” icon in the friends list) in either one of these two errors: (1) “UNable to join” which eventually might work after waiting a minute or trying multiple times or logging out and in from battle net (2) “Invalid password” error which cannot ever be recovered from unless the host restarts the SC Remastered app. This is on all players’ US West server, profiles, accounts. Very annoying.
(-> private games, password protected)