Facebook can be disconnected from dlvr.it for two main reasons:
1) If you change your password on Facebook, all applications which are granted Offline Access (the ability to post when you aren't actively accessing the site in a browser) have that permission revoked.
2) You have revoked the authorizations granted to dlvr.it.
To resolve either of these issues, simply reconnect your account with Facebook.
You can also set up alerts so that dlvr.it will notify you if we have lost Facebook authorization.