I think these instructions only work for communities someone on your instance has already subscribed to. Instead, try going https://lemmy.world/search and entering the full URL for the community ( https://kbin.social/m/LucidDreaming ). It’ll spin for a little longer than usual but it should show up in the search results.
Edit to add: The community will probably appear empty, however… new posts will show up, but anything from before the you subscribed probably won’t. If you want to reply to a particular comment, though, you can make it show up by searching for its full URL.
The mag stripe should only be accepted if the terminal doesn’t support chip or if the chip read fails a few times. I still come across stores without chip readers every so often.