I wanted to update one of my WordPress sites from 4.2.2 to the latest but WordPress did not show me there is a new version available even though WordPress is already on version 4.3.
If this happens to you the first thing you should check is to see if there is this line in your wp-config.php file :
define( 'AUTOMATIC_UPDATER_DISABLED', true);
In my case it was, so I set it to false however it sadly didn’t resolve the issue.
If the same thing happens to you then I suggest you to install this awesome plugin (just look at the ratings):
It immediately found out that WordPress code files were modified by cPanel (most probably if you installed WP via your hosts cPanel), which added few lines to core files that prevent WordPress to show updates (something with incompatibility). Word Fence then offered a bulk replace and replaced these modified files with the clean WordPress core files. Refresh and WP immediately offered and found update to latest WP.