If no one from your instance has subscribed to that remote community yet it won’t load. It’s a quirk of how federation works. Once a single person from your instance subs to that community then your instance will begin to sync and federate content. To get around this, the easiest way is to:

• open the web browser and go to lemmyverse.net
• Click the home icon (shapes like a house) and set your home instance
• Then search for the community you want to subscribe to
• Open the link and it’ll open the community in your home instance where you can subscribe

If that still doesn’t work then go to your home instance community search page and search the full URL of the remote community. You may have to search for it twice for it to show up. Then you can hit subscribe. Once you do this, not all content will be fetched retroactively. I think just a few weeks of posts and comments, but all future content will federate properly

Edit: when I click the link in your post in sync, it opens just fine for me