Hi Rheebo - There were a few changes within the 4.1 release and you will probably want to upgrade to that version for full support with Facebook. Between the 4.0 and 4.1 release Facebook added / changed how their OAUTH 2.0 API integration worked and we had to modify this within our module to fully support the latest versions of Facebook API.
After upgrading, you might also want to go step by step through this tutorial:
http://www.datasprings.com/news/blo...dotnetnuke Thanks,
Chad