Why are my Minecraft maps not showing up?

I’m having problems with getting Minecraft maps. Some of them work, but others don’t. I’m trying to get the "Titanic Survival 2" map but it just won’t show up.

I’m doing everything correctly: downloading the file, extracting the .zip, and putting it into my saves folder. But whenever I launch Minecraft and look in my singleplayer worlds, it’s not there. I’ve tried downloading it from different sites, opening it with different installations, and more, but nothing is working. I’m confused because some maps work but others do not.