CloudPanel troubleshooting-common issues and fixes

Most CloudPanel site issues come down to one of five things: a PHP-FPM process that has crashed, an Nginx configuration error, DNS not pointing correctly, a code error in the application, or a database problem. This guide covers the most common scenarios.

502 Bad Gateway

A 502 error means Nginx received no response from the PHP-FPM backend. The site's PHP process has crashed or is not running.

Fix steps:

1. In CloudPanel: go to Admin → Services and restart PHP-FPM for the relevant PHP version
2. Or via SSH: systemctl restart php8.1-fpm (replace with your PHP version)
3. Check the PHP-FPM error log: tail -50 /var/log/php8.1-fpm.log

Common causes: memory exhausted (PHP-FPM killed by OOM killer), a runaway script consuming all workers, or a PHP syntax error after a code deployment.

500 Internal Server Error

A 500 error is usually a PHP application error. Check the Nginx error log for the site:

tail -100 /home/SYSTEM_USER/logs/yourdomain.com.error.log

Look for PHP Fatal errors, file permission problems, or "no input file specified" errors. Common WordPress causes:

• A recently updated plugin or theme with a fatal PHP error-disable via FTP/SFTP by renaming the plugin folder
• Exhausted PHP memory limit-increase memory_limit in CloudPanel PHP settings
• Corrupted .htaccess-CloudPanel uses Nginx so .htaccess is not read, but a malformed Nginx vHost will also cause 500 errors

SSL not issuing

Let's Encrypt requires the domain to point to this server before validation. Check:

1. Run: dig yourdomain.com A +short-output should be your CloudPanel server IP
2. If using Cloudflare, ensure DNS is set to "DNS only" (grey cloud) during certificate issuance
3. Confirm port 80 is open: ufw status | grep 80
4. Check the acme.sh log: tail -50 /root/.acme.sh/acme.sh.log

Site not loading after DNS change

DNS propagation can take minutes to hours. To confirm the issue is propagation (not a configuration error):

• Use the UnderHost DNS Check tool to see what IP the domain currently resolves to
• Test the site directly via IP: curl -H "Host: yourdomain.com" http://YOUR.SERVER.IP/
• If the site works via IP but not the domain, DNS has not propagated to your location yet-wait and retry

PHP errors after version change

After switching PHP versions, some plugins or application code may not be compatible:

• Check the site error log immediately after switching: tail -50 /home/SYSTEM_USER/logs/yourdomain.com.error.log
• Look for "deprecated function", "undefined function", or "syntax error" messages-these point to the incompatible code
• If the site breaks completely, revert to the previous PHP version in CloudPanel until you can update the incompatible plugin or code

Database connection error

WordPress showing "Error establishing a database connection":

1. Check wp-config.php-confirm DB_NAME, DB_USER, DB_PASSWORD, and DB_HOST are correct. DB_HOST should be 127.0.0.1
2. Verify MySQL is running: systemctl status mysql
3. Test the connection manually: mysql -u DB_USER -p
4. Check disk usage-a full disk will stop MySQL from writing and cause connection failures: df -h

CloudPanel panel not loading

If https://YOUR.IP:8443 does not respond:

• Port 8443 may be blocked by the firewall-SSH in and run: ufw allow 8443/tcp && ufw reload
• The CloudPanel service may be stopped-SSH in and run: systemctl start clp && systemctl status clp
• Check the CloudPanel log: journalctl -u clp -n 50

Where to find logs

Related: How to create a website in CloudPanel | How to access CloudPanel on your UnderHost VPS | How to create and manage databases in CloudPanel | How to connect to your VPS via SSH | SSL certificates in CloudPanel-Let's Encrypt free SSL | How to migrate WordPress to a CloudPanel server

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