Hi,
It's because of the very annoying outgoing federation issues we have now on Lemmy 0.19.1.
All incoming data works very well but outgoing doesn't get sent until a restart of the Lemmy software, and then only once after restart. We will do a quick restart a couple of times per day and then your comments, posts etc will federate but of course it's really annoying with that long time in between your activity and others seeing it.
Hopefully there is a fix from Lemmy developers after new years. It has a bad idea to upgrade Lemmy before Xmas, and lesson has been very learned, believe me. :)
We had to remove the scheduled restarts since they didn't work reliably and brought the server down. So they are not in effect right now. We do manual restarts a few times per day only.
Still hoping for a fix from Lemmy devs soon...