This reauthentication will make sure that your social profile and CoSchedule are communicating correctly again. If you have messages that have failed due to reauthentication errors, those messages will need to be rescheduled.
To reauthenticate a social profile, go to Calendar Settings > Social Profiles.
On the Social Profiles page, you will see an error message on the social profile you need to reauthenticate. Go into the Social Profile's advanced page and click Reconnect Account to start the process of reconnecting your social profile.