I'm using the latest version of wp-Foro, along with the AddOns Embeds and Advanced Attachments.

Whenever we try to post a link to a Facebook post, the URL does not appear within the forum post at all, nor does a preview of the post appear. 

If I refresh the page, I can briefly see a glimpse of the Facebook URL, but once the page loads, there is no link there - just empty space in the post. 

When we post a link to a Twitter post, a preview of that tweet appears without a problem.

I'm not sure if this "bug" is a result of one of the AddOns, or if it is a bug with the new version of wp-Foro. 

This is happening in both forums I maintain (each on a completely different website). 

Any ideas how to resolve this problem?

Just as a test here, here is a link to a Facebook post - 
https://www.facebook.com/TheDrawingBoard3/posts/610330692742092?__xts__ [0]=68.ARCQeyXbrZFh5PDpX2CaZV_zoSWKcmg4Aj443HmeyiyuN-BwIGWSXKbgVSrSp2RK4AUZTJmnWeZy6bHYJZBcgX3uT2xAbEuj9esMBYtQ2qbIUXjQZcSDVgdnPIsv7_-KundPyLhLfeJ-QGGt0v7RQQXjQnfg0DQLCVuWBeo8YysQNfBWFIB3b4-rwqPBI96lHjwa9eNHmRG9_OswsG36pp8CPemomM8FJXgNUHMF3CFIzS0ub8sld31UVXDXpcQRoP0gQt3IOuRp9Db3FDrp1YWaiN0TdFCDlWY1luBnNz7f0LXlZ14M7dQa7hlMT77CXYvaYzUtH6YJNCprmebtlCw&__tn__=-R

Here is a link to a Twitter post - https://twitter.com/3DrawingBoard3/status/1104120216307617798

EDIT TO NOTE: After posting this, I see that the URL to the Facebook post appears here in this forum (no preview, but at least the URL appears). In the forums I maintain, I post the URL exactly as posted here, and once the forum post is posted, that URL link is NOT there - it just disappears. The Twitter URL turns into a visual preview. I've attached a screenshot to show you what the post looks like.