If you are having issues with your Facebook Lead Ad direct integration with Follow Up Boss here are some common ways we found to remedy the issue.

This Facebook Page is no longer available for your account to subscribe to

This happens when a particular Facebook page that you were previous subscribed to has either been deleted or your access to a page has been disabled. When this happens you'll see an information message on the Facebook integration card. 

If you still need access to this page you'll need to contact the Facebook Page owner admin to grant you permission again for this page you were previously subscribed to. Once they have added you back you can then reconnect your account to that page. Facebook Lead Add Direct Integration

If otherwise this page is no longer needed for Lead processing, you can click on update page settings to reset your connection and that expired Facebook page will be removed from your Facebook integration page.