Unable to access wp-admin

Solution:

It looks like you’ve done the standard troubleshooting tests. Try adding the following lines to your active theme’s functions.php file.

function flush_my_rules() {

    flush_rewrite_rules();

}

add_action('init','flush_my_rules');

Make sure to keep the following lines in your wp-config.php file.

define('WP_HOME','http://example.com');
define('WP_SITEURL','http://example.com');

Then try visiting your homepage first, then your /wp-admin/ page. See if you continue to get a 404. If you do, try visiting the /wp-login.php page, and see if logging in via there continues to return a 404.