It is not dependent on Bubble but on Google - it takes some time for Google to crawl and index your app, up to a few weeks in some cases. Just make sure you have the following set up correctly in settings:
- General > Favicon
- SEO/Meta tags
- Title, Site name, Description
- Expose a sitemap file (checked)
If you are not using Google Search Console (free), set it up for your app and then keep track of how/when the app is index.