Snippet slug on page

Replies: 0

I have been editing my front page of late as I recently installed Yoast SEO. When I type in the slug of the URL in the snippet editor, all goes green on the bullets. But when I save the page, the slug goes away and the SEO score changes to orange.

Also I just today changed the title of the front page. Do I need to do anything with the sitemap index?

Why?

TNX
Peter