Dan - It's at https://apps.wikitree.com/apps/ashley1950/ancestorexplorer/
I just added a mapping feature and rebranded it as Ancestor Explorer. The name and description has not yet been updated on the Apps page that Lucy mentioned, but if you go to the old url (through the Apps page or otherwise), you are automatically redirected to the new version.
Re 24 generations - I was initially confused by this, but I think I figured it out. The app is not giving you a complete set of ancestors 24 generations back (or even 21, 22 or 23 generations back), just some of them. The reason why the app gives you some ancestors 24 generations back is that the app gives you every ancestor who is within 20 generations by any ancestral line. However, an ancestor who is 20 generations back by one line might be 21, 22, 23 or even 24 generations back from you by a different line. So any ancestor the app gives you who is 24 generations is also an ancestor who is 20 generations back by some other line.