No CSS being loaded on backend

I have a WordPress installation on AWS and I was facing an issue that authors are not able to submit content like media in one go and a time-out error occurs. After refreshing the page 5-6 times authors are able to upload content again.

To mitigate this issue, I deactivated all the plugins and upgraded to WordPress 4.0 from the back-end, which also raised a problem and I had to rerun the update manually.

So I downloaded the latest WordPress Zip and followed the instructions as mention on http://codex.wordpress.org/Updating_WordPress.

Finally, in the last step, when I refreshed the browser window, it asked that the database needs an upgrade too. So I followed the on-screen instructions and logged into my WordPress.

After logging in, the WordPress back-end looks like in the following screenshot:

It looks as if no CSS being loaded. How can I solve this issue?

Adding these two lines to “wp-config.php” worked for me. I had the same issue.

define( 'CONCATENATE_SCRIPTS', false ); 
define( 'SCRIPT_DEBUG', true );

Also, remember to clear cache on server and browser.