This error usually occurs if you've skipped some or all of the permissions requested by Facebook.
In order for us to be able to retrieve information so that a service can be added successfully and that your posts will be sent through to the relevant social site, you will always need to accept All permissions which are requested.
To resolve this for Facebook Services, please do the following:
1. Make sure you're logged out of Facebook in all browsers and tabs.
2. Look to add the service again.
3. You should then be directed to log into the appropriate Facebook account, please ensure to allow all permissions requested.
4. Your Pages or Groups should then be displayed, check your settings are correct and then look to save the service.
Please note that, in the case of groups, you will also need to be an admin for the group you're looking to add in order to do so and not just a member of the group.
If you're still experiencing issues once you've done this, please contact firstname.lastname@example.org.