Homepage returns an error status
Effort to fix: Moderate (a few hours)
Why it matters
Search engines drop pages that answer with 4xx/5xx, and visitors see an error instead of your site.
How to fix it
Find out why the homepage returns an error (server logs, misconfigured routing, a missing index page) and make it return HTTP 200.
On WordPress
Re-save permalinks (Settings > Permalinks) to rebuild rewrite rules, and check that a static front page is published if you use one.