I still see things from 7 days ago at the top when I sort by “active” while other posts have much more activity and are newer. “hot” is the same thing with most posts from 5 days ago.
On https://lemmy.ml/ and https://lemmy.world/ it seems like sorting by “active” is working, there are posts from around 3h ago that have 100 upvotes so that I would consider “active”.
It’s a bug. It’s known about. It’s in the process of being fixed.
The servers throw an error and stop re-sorting active and hot, so when you browse there it’s showing you the top results from days ago.
The instances with working sorting are doing so because they are actively restarting their servers to update their sorting.