Joe (Technical Community Coordinator) (Matillion Limited) helped to get the Matillion Configuration steps for Facebook OAuth updated. Please try this out.
https://matillioncommunity.discourse.group/t/need-facebook-side-of-oauth-setup-steps-for-matillion-oauth-to-connect-successfully/1257
I am still not there 100% as i dont have a domain name for the server + Facebook is not accepting my public ip, but a better progress has been made.