Error 521 is a Cloudflare error that occurs when a website’s origin web server is down or unreachable. Here are some steps you can take to fix this error:
- Check the origin web server: Make sure that the origin web server is running and that it can be reached by Cloudflare.
- Check the DNS settings: Make sure that the DNS settings are configured correctly and that the website is pointing to the correct IP address.
- Check the firewall settings: Make sure that the firewall is not blocking the connection to the origin web server.
- Check the load balancer: If you’re using a load balancer, make sure that it is configured correctly and that it is not blocking the connection to the origin web server.
- Check the SSL certificate: Make sure that the SSL certificate is valid and not expired. Also, check if the certificate is trusted by the browser.
- Check the Cloudflare configuration: Make sure that the Cloudflare configuration is correct and that the website is being proxied through Cloudflare.
- Clear the browser’s cache: Clearing the browser’s cache may help to resolve the issue if the error is caused by a cached version of the website.
- Contact the support: If none of the above steps have helped, you may need to contact the Cloudflare support team for assistance.
It’s worth noting that the cause of this error can be specific to the application or website, so it is important to check the documentation of the application or the website to see if there is any information about this error and how to fix it.