Sometimes users on Facebook have privacy settings that prevent ELISA from obtaining their name and writing to them.
In fact, it also means that ELISA cannot write to the customer. A customer will often get in touch and ask why they have not received an answer. And without a response, the customer has not been referred products or shopping cart.
Solution
This setting can be changed by the customer in their own Facebook settings here:
https://www.facebook.com/settings?tab=applications&ref=settings
DO NOT TURN OFF - This screenshot here below indicates the correct setting if you want ELISA to be able to send messages to you.
If you are in contact with the customer, you can transfer the link to cart by any other communication form. And maybe the link to this guide too.