Most instance admins ban porn for legal reasons. You need to find an instance that allows porn. Lemmynsfw.com is a porn instance (and the home instance of the person I replied to). Note that you also need to be logged into a lemmy account that has the “view nsfw” option enabled in the lemmy user settings. If you’re not logged in, or that setting is set to hide nsfw, no posts will show. I find it easier to just create a separate account on a porn instance rather than try and join from your home instance, which might have settings making it difficult to see anything.