wpForo.com FB APP keys were configured 3 years ago, so they are outdated now. So just try to configure your FB APP better, your issue has is not related to ours. We'll configure wpForo FB app keys when we find an appropriate time for it.
In case you want to say thank you !) We'd really appreciate and be thankful if you leave a good review on plugin page. This is the best way to say thank you to this project and support team.
