If you go to that website directly without logging in, do you see the posts? It is entirely possible that there are no posts there - sports communities aren’t getting a lot of non-bot traffic.

If there are posts, how old are they? If you are sorting by top, you won’t see any posts that were posted outside your selected time frame.

If neither of those are the issue, I’d blame Lemmy.world. They have cloudflare rules that block other instances without listing them as defederated. It is possible they’ve moved to a whitelist or some other trust based model that blocks new instances by default.

This is a side effect of them having been under a near constant DDOS and other cyberattacks, and so is definitely defensible, however it ultimately hurt the UX for me to the point that I just moved to a different instance.