Google+ Token expired

On Google+ the tokens can expire in three ways:
- end of time: generally after 60 days from the last access the token gets deactivated
- Change Password: The token is linked to the old password, if the change is necessary to log in again.
- Request threshold exceeded: It can happen if the user has passed a number of requests for the token.

To reauthorize Google+ just login to your site, click on Connected Social Networks and re-connect the expired social.