If you encounter a secure connection issue on your website, there are a few possible reasons. Here are the most common ones and how to fix them:
If you have just registered the domain name, or if you have recently pointed it to your website, wait a few hours for propagation to complete. Next, clear your browser's cache before visiting your website.
If your website is created with Hostinger Website Builder, make sure it's published.
In case your website shows an ERR_SSL_PROTOCOL_ERROR message, it means that an SSL certificate is either not installed or not working properly on your website. Here is a dedicated guide: How to Fix ERR_SSL_PROTOCOL_ERROR.
Add https:// to your URL in the browser's address bar. If it loads correctly, meaning, there's a padlock next to the web address, then you only need to force HTTPS so that the visitors would land on the secured version of your website by default.
If your website is accessible through HTTPS, but its layout is distorted, it's likely due to mixed content issues. Refer to this guide for more details: What to do if a website shows a mixed content warning.
You can also refer to this video tutorial for more options: