Failed to Log into Admin Panel after Upgrading to WordPress 3.5.2

Be very cautious on clicking the “Upgrade to 3.5.2” button on your WordPress website. I have 10 successful upgrades, but 8 failures. It is not a disaster, because it is easy to fix.

The Symptom

404-error-page-not-foundThe trouble is at the back-end, aka the admin area. Because you are accessing the upgrade from admin panel, the big “404 error – page not found” will catch your eye immediately. The good new is, it only effects the back end.

When this happens, the URL is like:


While this happens, you are not able to access the admin panel.

The Solution

  1. Download and extract the WordPress 3.5.2 package to a local folder.
  2. Link to hosting server through FTP client.
  3. Delete the WP-admin folder in the failed upgrade, (or rename it to wp-admin.bak)
  4. Upload wp-admin folder (including all subfolders, files) manually from local to web server.

After finish downloading, you can go directly to access wp-admin in browser. The upgrade will continue by prompting you to upgrade the database, click UPGRADE to finish it. So I have a feeling that, the upgrade failed at database upgrade.

Please take a note: You can also do “Upload and Overwrite”. Your website may not accessible during the time the wp-admin being uploaded. Because in some FTP clients, upload & overwrite operation, means delete existing first and upload later.

To avoid website downtime, I normally upload the wp-admin folder to a subfolder. After finish uploading, rename the existing wp-admin to wp-admin.bak, then move the newly uploaded wp-admin into position. Doing so, the website has less than few seconds downtime. In most case, undetectable.