First and foremost, in the past few months, Facebook has made changes to their terms of service, as well as those of Instagram (which Facebook owns).
Beginning on Friday, February 12, 2016, these are the changes to be aware of:
Your previously connected Facebook or Instagram address books will be disconnected and removed from FullContact.
Going forward, you will no longer be able to connect a new Facebook or Instagram address book to your FullContact account.
However, if you need a backup file of your contacts (which include Facebook and Instagram), please reach out to our Support team. While we understand these changes may be frustrating, FullContact is committed to building powerful tools to help you build relationships with your network. We'll continue working on new ways to keep your contacts in sync, up-to-date, and accessible everywhere you need them. Also, unlike some other services, we're committed to making sure that your data is always portable - you can export all your contacts whenever you like. They belong to you.
Keep in mind that you can still add your Facebook friends' contact information to your contacts from the Facebook app on your iPhone or iPad. These instructions are listed below.
iOS Workaround for adding Facebook information to your contacts
Currently there is no Android workaround, but there may be in the future when FullContact is able to sync directly with device contacts on an Android device.