Why does the WordPress Navigation block show one menu in the editor and another on my live site?

You’re probably editing a different Navigation block or header template part from the one the live page uses. In the Site Editor, open the actual template for the affected page, then open its Header template part and use List View to select the Navigation block. WordPress shows the attached menu name there, and one Navigation block can be assigned a different menu than another. Save both the menu and the template/part, then clear any page, host, or CDN cache before checking the live site. If the mismatch is only on mobile, check the Navigation block’s display setting too. The editor preview can look right while the public page uses another template or a cached older version.