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I have added the production url in the private notes section of this post. If you click on the URL it will take to you to the exact post and when you click "Share" you will see the issue. It happens with all group posts.
i see. you mean group discussions, that blank popup returned error message:
Forbidden Access (403)
it must blocker at your site or server. please try to disabling it. maybe firewall? or your site preventing any external connection?
not sure, only server admin know it.