Our site has been working fine in the last week. Today, I can't add a new page to our menu. Clicking "Add to Menu" just produces a spinning icon that never disappears.

If I look at the Chrome console, I see:

POST https://www.example.com/wp-admin/admin-ajax.php?_fs_blog_admin=true 404 (Not Found)

There are no restrictions on /wp-admin or /wp-admin/admin-ajax.php in /.htaccess or /wp-admin/.htaccess.

I've Googled for this problem but most Q&A post relate to custom ajax calls.

In our case we're not making custom ajax calls.

Troubleshooting steps appreciated.

PS - I am waiting on the web host to check if mod_security is causing this issue.

  • 2
    Have you verified the file is unmodified and intact? And that the rest of the core WP files are unmodified? This is highly unusual
    – Tom J Nowell
    Mar 8, 2019 at 3:16
  • 1
    Thanks @TomJNowell, I uploaded a fresh copy of admin-ajax.php and that solved the problem straight away. Add an answer if you like.
    – Insight
    Mar 8, 2019 at 3:19

2 Answers 2


Your /wp-admin/admin-ajax.php might have been modified by another php file or plugin. Try downloading a copy of your wordpress version and overwrite admin-ajax.php with the original source file. If that doesn't work, try deactivating your plugins (or theme) one by one until you notice a difference.


I have descovered that for me this occurs because my script has a long run time chrome has a 5 minute timeout period. The script is ajax and keeps running even when the browser gives up on it. Oh I just saw you are not dealing with a custom ajax call, in that case this will not help.


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