404 admin-ajax.php error url=/checkDocument

Host Firewalls

Occasionally, hosting companies will setup a firewall on your site that is intended to protect your site but that also has the adverse affect of blocking access to admin-ajax.php. If you are having trouble with ajax, check if your host has a firewall and disable if it so. If ajax begins working after disabling the firewall, you have found the culprit. If ajax is still inaccessible after disabling the firewall, you can usually safely re-enable it.

Rules in Your .htaccess File

The .htaccess file used on apache servers can sometimes include special rules that are designed to protect your site from attacks. Occasionally these rules are applied a little too generally and unintentionally disable access to admin-ajax.php. If your ajax is not working, check to see what rules your .htaccess file contain. If there are any rules beyond those shown below, remove them and see if ajax begins working again.

Your .htaccessfile will usually contain rules that look like this (these are perfectly safe and normal):

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule># END WordPress

When I google this part of the Query String – “action=proxy_atd” I found 2 search results that show this has to do with Jetpack > After the deadline module. My guess would be that you would need to resave your jetpack After the deadline module settings to update them after you have done a migration. Most likely the jetpack After the deadline module settings still have your old site settings saved and once you update the settings they will be current to your newly migrated site.