robots.txt disallows the entire site

What this means

The robots.txt group that applies to this crawler carries a Disallow: / rule, and re-testing the root path under the parser's full precedence rules confirms it is genuinely blocked rather than overridden by a sibling Allow: / of equal specificity. Search engines that honour the file stop fetching the site altogether, pages already indexed decay out of the results, and no new page can be discovered. The usual cause is a staging environment's robots.txt deployed to production by accident.

How to fix it

Remove the Disallow: / line, or narrow it to the paths that genuinely should stay out of the crawl. Where the aim is to keep pages out of search results rather than out of the crawl, use a noindex meta tag or X-Robots-Tag header on those pages instead — a disallowed page is never fetched, so its noindex is never even seen.

Fix effort

This check needs a developer fix: it turns on a routing, hosting or infrastructure decision that no automatic edit can make safely.

Authoritative source

https://developers.google.com/search/docs/crawling-indexing/robots/create-robots-txt