There could be a few reasons. The content on your website might not be relevant enough for the topic you searched for. The competition might be too strong and push your website too far down the search results. Your website might not be giving the correct instructions for search engines to understand and process the content.
To find out the reason, start by asking Google to show you only the results it has listed from your website. For this, type in the search box:
site:your-site-name.com. If nothing comes up, Google might not even know your website exists yet. Next step is to use the Search Console and register your website (and sitemap.xml) to inform and monitor how Google understands your website.
If you still can’t get it to work, I can do a Website Review and fix it for you.