EDIT: I checked your lemmy.world instance with the same settings https://lemmy.world/home/data_type/Post/listing_type/All/sort/Hot/page/1 and indeed all posts seem to be old. It’s something to do with your instance maybe. I suggest meanwhile you use All Top Day instead. This will ensure you get top posts of the past 24h.
Difficult to say why it doesn’t work for you. What I get is 10h, 2h, 2h, 1h, 4h for first 5 posts. I am using All Hot.
https://lemm.ee/home/data_type/Post/listing_type/All/sort/Hot/page/1
EDIT: I checked your lemmy.world instance with the same settings https://lemmy.world/home/data_type/Post/listing_type/All/sort/Hot/page/1 and indeed all posts seem to be old. It’s something to do with your instance maybe. I suggest meanwhile you use All Top Day instead. This will ensure you get top posts of the past 24h.