Possible Reasons:
- Your site is just new;
- Your site was not yet indexed by Google.
How to submit your site to Google?
- Navigate to Google Search Console using this link https://search.google.com/search-console
- Click “Add Property”
- Select domain if you have subdomain(s), otherwise select URL prefix and add your root website link.
How to test?
In the Google search field, type site: and your website link.