A 500 Internal Server Error means something went wrong on the server side. In WordPress, this is usually caused by a corrupted .htaccess file, a plugin conflict, or a PHP memory issue.

Step 1 — Regenerate the .htaccess file

A corrupted .htaccess is the most common cause.

1. In cPanel File Manager, navigate to public_html.
2. Enable Show Hidden Files in Settings.
3. Rename .htaccess to .htaccess_old.
4. Reload your website. If it loads, the .htaccess was corrupted.
5. Log in to WordPress admin and go to Settings → Permalinks.
6. Click Save Changes without changing anything. WordPress will create a fresh .htaccess file.
7. Delete .htaccess_old.

Step 2 — Deactivate all plugins

1. In File Manager, go to public_html/wp-content/plugins.
2. Rename the folder to plugins_disabled.
3. Reload your website. If it loads, reactivate plugins one by one to find the culprit.
4. Rename the folder back to plugins when done.

Step 3 — Increase PHP memory limit

1. Open wp-config.php in File Manager.
2. Add this line before /* That's all, stop editing! */:
   define('WP_MEMORY_LIMIT', '256M');
3. Save and reload.

Step 4 — Check PHP error logs

1. In cPanel, go to Metrics → Errors.
2. Review the most recent error entries. They will point to the specific file and line number causing the 500 error.

Step 5 — Re-upload WordPress core files

If none of the above worked, a corrupted WordPress core file may be the cause.

1. Download a fresh copy of WordPress from https://wordpress.org/download.
2. Extract the ZIP file.
3. Upload all files except the wp-content folder and wp-config.php to your public_html folder, overwriting existing files.