While the issue has seemingly been resolved as of November 17, should the problem arise once again, there's a fix that players can use to resolve the issue. Those who want to invite friends must create select the Channels  tab, create a channel, then have people join in.

There might be corrupt files in your installation directory which could be the potential cause for the Logging into Online Services  error in Warzone 2. You can scan and check the files on both Steam and Battle by selecting the game, going to the settings, and searching for the scan and fix option.