If I go to the Plugin Repository (/admin/plugin-repository/plugins.action) and click on the + next to the plugin named Atlassian Plugin Repository, I get a description. The description has two links named Confluence Plugin Repository. Both links take me to a page with a Page Not Found error and this statement: "The page you were trying to reach does not exist. You may want to try a search, or browse the site to find the page you were looking for."