I am wondering if this is to do with account that the Kbin.Social server has noticed.
Fediverse servers don't notice all posts from all accounts from all other servers, as the resources needed would cost a fortune.
There's a set of rules which determines if a server notices an account or post (https://fedi.tips/which-posts-and-accounts-can-i-see-from-my-server/).
Perhaps the account you are testing it from hasn't been noticed by Kbin.social? Have you followed the Mastodon account you tested with from your Kbin account?
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