Facebook not showing

So it worked before? Did you do any changes on your site or theme in the meantime?

Yes, updates.

Since it is in a iframe, I cannot track down the problèm.

Ok. We tried some CSS changes, but it also didn’t fix it. Please ask your theme developer about it as it happened after the update.

The theme was not updated. Plus, CSS cannot modify the appearance through iframe.
I can give you a list of updater plugins if you wish.

Please disable the other plugins one by one to see which one is the culprit.

Did you find out which plugin caused the issue?