Why are my posts not indexed?

Work through these in order.

1. Your robots.txt lists your blog's sitemap

Search engines find your posts through your sitemap. They find the sitemap through the robots.txt file on your main domain.

Your blog is at	`example.com/robots.txt` should contain
`example.com/blog`	`Sitemap: https://example.com/blog/sitemap.xml`
`blog.example.com`	`Sitemap: https://blog.example.com/sitemap.xml`

The Custom Domain page checks this for you. If Robots.txt says Needs attention, click View details for the exact line to add.

2. Your site is in Google Search Console

Add your website to Google Search Console, including the subdomain if your blog is on one, and submit your sitemap. See Connect Google Search Console.

3. Your posts are worth indexing

Google decides not to index pages it considers thin or low quality. Write posts that answer a real question in depth. The SEO best practices panel in the editor helps.

Also check

The post is published and deployed. Drafts are never online.
You have not ticked Do not index for that kind of page in Settings > SEO.
New posts can take days or weeks to be indexed. In Search Console, use URL Inspection and Request Indexing to speed one up.