ERR_SSL_PROTOCOL_ERROR - if you see this error, it means that the SSL certificate for your website is not installed yet or is having issues. If the certificate is already installed, our ERR_SSL_PROTOCOL_ERROR article will help you

Try adding HTTPS:// to your URL. If it works and you see a padlock, then all you need to do is force HTTPS for visitors to see the secured version of your website by default

If your website is available via HTTPS, though it looks corrupted, it means you have some mixed content. You can fix it by following this guide: What to Do if Your Website Shows a Mixed Content Warning