People search will exclude users who identify they do not want to be included in search results (an option on the settings page).
People search (and profile fields) require the Read Profiles permission. Without this permission, no results will be provided because the accessing user does not have permission to view the user details.
The search index will need to update. If this doesn't occur automatically, you can force a reindex of users by going to Administration > Site > Search, go to the Include tab, unselect "Users", Save, reselect "Users", Save. When the search index next updates, searchable users will be visible.
Note that this is subject to the Include in Search option.
