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When a WordPress site misbehaves — white screen, 500 errors, broken features — systematic debugging finds the cause fastest. Here’s how to do it with cPanel and the WordPress Toolkit.

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Step 1: Check the error logs

  1. In cPanel, open Errors (Metrics section) for recent Apache/PHP errors, and check the error_log files that PHP writes into your site’s directories (visible in File Manager, typically in public_html or the folder where the error occurred).
  2. The most recent entries usually name the failing file — often a specific plugin or theme file. That’s your prime suspect.

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Step 2: Enable WP_DEBUG logging

Edit wp-config.php (File Manager → Edit) and add above the “That’s all” line:
Errors, warnings, and notices are now written to wp-content/debug.log without being shown to visitors. Reproduce the problem, then read the log.
Remove or set these back to false when you’re done — debug logging on a live site grows the log file and can leak information if misconfigured to display.

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Step 3: Isolate plugins and themes with the Toolkit

The classic conflict test, made painless by WP Toolkit — no wp-admin needed (useful when wp-admin itself is broken):
  1. In cPanel → WP Toolkit, open the site’s card.
  2. Under Plugins, deactivate all plugins. Site fixed? Reactivate them one at a time until it breaks again — the last one activated is the culprit.
  3. Still broken with all plugins off? Under Themes, switch to a default theme (Twenty Twenty-Four). If that fixes it, the theme is at fault.
On Deluxe, do this on a clone instead of the live site for zero risk.

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Step 4: Check PHP version and limits

  • Fatal errors mentioning syntax or undefined functions after an update often mean a PHP version mismatch — try the version the plugin/theme requires.
  • “Allowed memory size exhausted” → raise memory_limit; timeouts → raise max_execution_time.

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Step 5: Common specific fixes

  • White screen after editing functions.php: fix or revert the edit via File Manager — the log from Step 1 gives the exact line number.
  • Too many redirects: check siteurl/home values (must both be https and consistent) and any redirect plugins.
  • Changes not appearing: clear all caches — LiteSpeed Cache/plugin cache, and browser cache.
  • wp-admin locked out entirely: use WP Toolkit’s login button; if even that fails, deactivate plugins via the toolkit and retry.

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When to hand it over

If the logs point at something server-side, or you’re stuck, open a support ticket with the exact error text and the timestamps — our team can check server-level logs that aren’t visible in cPanel.