Why is my WordPress site not loading and showing a 521 error?

I. Understanding Cloudflare 521 Errors First, understand this: The "521 error" you see is actually a prompt from Cloudflare (your website likely uses this CDN service), indicating Cloudflare cannot connect to your origin server. Simply put: Visitor → Cloudflare (successful) → Your server (failed). This error is largely unrelated to your WordPress content itself and primarily concerns your server's operational status. II. Four-Step Troubleshooting for Beginners 2.1 Step 1: Check Server Availability Log into your website hosting platform's control panel (e.g., cPanel, Baota Panel, or your host's backend). Locate options like "Service Status," "Restart Services," or "Server Monitoring." Verify if your web service (typically Apache or Nginx) is running normally. If it shows "Stopped," try clicking the "Restart" button.This is one of the fastest ways to resolve the 521 error. 2.2 Step 2: Verify Server Resource Usage Locate the "Resource Usage" or "Statistics" section in your control panel. Focus on three key metrics: Disk Space: If usage exceeds 95%, clean up files. Memory Usage: Persistently approaching 100% may cause service crashes. CPU Usage: Abnormally high usage may indicate issues. The simplest temporary fix is: Delete old backup files, clear cache directories, and disable unnecessary large files. 2.3 Step Three: Troubleshoot Firewall Misblocking If you recently adjusted server security settings, firewall rules may be misconfigured. Contact your hosting provider's support team with this request: "Please verify if my server's firewall (iptables/firewalld) is blocking connections from Cloudflare's IP range," and provide your server IP address. Professional support typically resolves this quickly. 2.4 Step Four: Investigate Database Connectivity Occasionally, database service issues indirectly cause web service crashes.Locate the "MySQL" or "Database Services" option in your control panel and check its operational status. If the database service has stopped, attempt to restart it. Note: It's advisable to pause website access before restarting. III. General Maintenance Recommendations For persistent and unstable 521 errors, we recommend: Contact Technical Support: Provide your hosting provider with screenshots of the error and its occurrence time—this is the most efficient resolution method. Enable Monitoring: Activate "Auto-Restore" notifications in the Cloudflare control panel. Perform Regular Backups: Ensure complete backups of website files and databases exist before troubleshooting. Important Reminder: During troubleshooting, temporarily avoid installing new plugins or modifying core files to help isolate the issue. Most 521 errors can be resolved by restarting the web service or contacting your hosting provider.