1. Indexing of search engine:
Post may take time to be indexed by search engines, if the homepage has newly been updated which may take google sometime to recognize the change and index the new content.
2. Low quality content:
If the quality of the content is low, your homepage may not show up on google and also not meeting the search engine guild lines.
Make sure that your site robots.txt is not blocking post description by search engine not to be crawled.
4. Content duplicate:
Post that has the same content with another post on other websites can make a homepage not to show on search engine results.
5. Improper meta tags:
If your meta tags are not proper such as title and description, it may cause your homepage not to show up on google search engine.
• TO FIX THIS PROBLEM
Make sure that your homepage is optimized with proper meta tags, content with high quality and free from content duplicate to be able to show up on google.