Mastodon caches things heavily (well at least niu does).
I moved the actor entry for @firstname.lastname@example.org (which currently hosts a WIP ActivityHub implementation) from /actor/shuga to /shuga and it hasn't corrected itself.
Note: I moved the actor entry to @email@example.com since it's for testing.
Welcome to your niu world ! We are a cute and loving international community Ｏ(≧▽≦)Ｏ !