It’s how federation works, if you are the first from your instance you don’t see posts, after some minutes the 2 servers communicate behind the scenes, and for your second visit everything looks normal. This is per instance, so it seems you were the first from lemmy.ca to click on that community.
TIL! Thanks! I’ve wondered why the F there are zero posts. That said, I’m on Lemmy.world and not constantly on my phone, so that’s not a good sign.