If you go here: https://piefed.social/home/active/all

It just looks like its showing the most recently commented post. That probably isn't how "Active" is suppose to work. On Lemmy, it works like this: https://join-lemmy.org/docs/users/03-votes-and-ranking.html

Active (default): Calculates a rank based on the score and time of the latest comment, with decay over time