Updated
1. Confirm it is really not indexed
Use the URL Inspection tool in Google Search Console. It is the only authoritative answer, and it tells you which of the cases below you are dealing with: not discovered, crawled but not indexed, or excluded by a tag.
A site: search in Google is a rough indication only and regularly misses pages that are in the index.
2. Make sure robots.txt is not blocking the page
A Disallow rule that matches the URL stops Googlebot from fetching it. This happens most often when a staging rule such as Disallow: / is deployed to production, or when a broad rule like Disallow: /blog catches more paths than intended.
3. Look for a noindex tag or header
A robots meta tag with noindex, or an X-Robots-Tag: noindex response header, tells Google to keep the page out. CMS plugins and framework defaults sometimes add it to whole sections, such as tag archives or preview deployments.
Note the interaction with step 2: if robots.txt blocks the page, Google cannot see a noindex tag on it at all.
4. Check the canonical tag
If the canonical on the page points to a different URL, you are asking Google to index that other URL instead. A template that hardcodes the homepage as canonical on every page is a classic way to make an entire site disappear.
5. Put the page in your sitemap
A sitemap is how Google learns about URLs it has not found through links. Make sure the page is listed, that the sitemap is valid XML, and that robots.txt or Search Console points to it.
6. Link to it from pages that are already indexed
A page that nothing links to is an orphan. Google may know the URL from the sitemap and still decide it is not worth crawling. Add links from relevant pages — a hub page, a related article, the navigation — using descriptive anchor text.
7. Be honest about the content
The status Crawled – currently not indexed means Google fetched the page and chose not to keep it. That is usually a quality judgment: the page is very thin, or near-identical to another page on your site or elsewhere. Technical fixes will not change that; making the page clearly more useful will.
For a new site, also allow time. Discovery and indexing can take from a few days to several weeks.
