Destiny 2 will receive an update tomorrow. Players will be required to log in to Destiny 2 again after installing the update. Please stay tuned to @BungieHelp for updates.
This came up in our clan just now where a Guardian with the German version of D2 was trying to join a fireteam with the English version of D2. He couldn't join because the German D2 couldn't recognize the word 'join'. Why not have it so that no matter what language the Join code is in a Guardian can join a fireteam. Again, just a suggestion.