英語ですが、以下に同じような質問がありますが、解決してないみたいです。
Facebook Social Connector not showing business page - anyone find a fix?
Tech Provider verificationの話題が出ていますが、これってユーザの設定ではないような気もします。
技術提供者アプリのアクセス認証プロセスの運用開始
I did notice that Facebook is now asking for a Tech Provider verification since we are trying to connect apps (Pardot social connector). However, we didn't create the app so I can't get the verification but Facebook will block all APIs without it. Has anyone run into that? I assume that could be the culprit. When I spoke with Salesforce help, they did say other customers were experiencing the same issue but had no resolution for it.