An HTTP status identifies where a request stopped. Record the exact URL, time, and code, then determine whether the problem affects one route, one domain, or the entire server.
400 Bad Request
The request could not be understood. Clear site cookies, check long URLs or headers, and inspect proxy rules.
401 Unauthorized
Authentication is required or invalid. Confirm credentials, protection rules, and application sessions.
403 Forbidden
Access was denied. Check ownership, permissions, index files, Access Protection, and server rules.
404 Not Found
The route or file does not exist at the active document root. Check spelling and capitalization, uploaded files, application routing, and WordPress permalinks. Apache transfers may require important .htaccess rewrites to be translated for Nginx.
405 Method Not Allowed
The route does not accept the request method. Check whether the application or form expects GET, POST, PUT, or DELETE.
408 Request Timeout
The client did not finish in time. Retry on a stable connection and inspect slow uploads or strict timeout settings.
413 Content Too Large
The upload exceeds a web or PHP limit. Review the Nginx request size and PHP upload and post limits.
429 Too Many Requests
A rate limit or security control is slowing repeated requests. Wait, then inspect automated clients, application limits, and firewall decisions.
500 Internal Server Error
The application failed while processing the request. Read its error log, then check PHP syntax, dependencies, environment values, ownership, and database access.
502 Bad Gateway
Nginx received an invalid response from PHP, Python, Node.js, or another upstream. Confirm the service and its configured socket or port.
503 Service Unavailable
A service is unavailable or the application is in maintenance. Check service health, resources, deployment state, and maintenance mode.
504 Gateway Timeout
An upstream did not answer in time. Look for slow queries, external requests, overloaded workers, or stopped processes before increasing timeouts.
DNS, connection, and certificate errors
DNS address not found means the hostname is not resolving publicly. Confirm nameservers and A/AAAA records. Connection refused normally means nothing is listening or a firewall rejected the connection. Certificate warnings indicate a missing, expired, mismatched, or not-yet-valid certificate. DNS and local domain configuration must be correct before adding SSL.
Troubleshoot in this order
- Record the exact message and time.
- Confirm DNS resolves to the intended server IP.
- Confirm the domain and document root exist in Website Manager.
- Review Web Stats, application logs, and Service Status.
- Check runtime choice, ownership, permissions, and application configuration.
- Correct the cause before retrying the same action.