Note the full hostname, request path, approximate time and action that failed. Avoid recording passwords or sensitive request bodies. Confirm that you can access the domain logs and application logs under your authorized subscription.

1. Open the domain Logs page in Plesk and narrow the time window around the failed request.
2. Select the relevant error log sources. Find the first meaningful PHP error and any related web-server message, rather than treating a later cascading warning as the original cause.
3. Reproduce the issue once when safe, using a harmless request or a test account. Compare the new log entry with the recorded time and URL.
4. For application frameworks, inspect their private application logs as well. PHP may only report that a process failed while the application log contains the actual exception.
5. Classify the result: syntax or type error, missing extension, memory exhaustion, permissions, unavailable database or failed upstream service. Change only the component supported by that evidence.

Repeat the same safe request after the change and check that no new matching error appears. Test an adjacent workflow so a local fix has not broken another part of the application. Keep a concise record of the original error and resolution.

If no PHP entry appears, the failure may occur before PHP runs, or logging may use another destination. Review the handler and logging settings without exposing errors publicly. Restore the previous application release if a recent deployment caused the failure. Share sanitized log excerpts with support, removing credentials, tokens and personal data.

• Choosing and changing a domain PHP handler in Plesk
• Diagnosing website errors with the Plesk log browser
• Adjusting PHP limits for one Plesk domain
• Installing PHP application dependencies with Plesk Composer

• Plesk: Log Files
• PHP: Errorfunc.configuration