When I tried to log in using the default /user and /user/login Drupal URLs, the form appeared to post data but looped back to it’s original state i.e. blank fields.
This was the same across all websites, all browsers and was the same for all users.
There was nothing in any of the error logs but a 404 in the access logs.
To fix this issue you need to edit your httpd.conf file, un-comment the following line:
LoadModule rewrite_module libexec/apache2/mod_rewrite.so
Then restart Apache using sudo apachectl restart command.
Hope this helps a few people out!