Can you give more details? What sort of group is this? Is it public or private? How large is it? How long has this been going on? What links are you trying to post that got blocked?
Just random guess but you probably triggered link spam rules. People posting the same link over and over. It looks a lot like a spam attack to an algorithm.
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[ 3.4 ms ] story [ 35.4 ms ] threadMods/Admins? That's not even a thing on FB more broadly, right?
Amazing this gets upvoted. User has absolutely no other pots/comments.