Hi, try to use this configuration (httpd conf file):
Alias /blog /var/www/html/wordpress
<Directory /var/www/html/main-site>
PassengerEnabled off
DirectoryIndex index.php
Options -MultiViews
AllowOverride All
order allow,deny
allow from all
</Directory>
I found this configuration here: https://iswwwup.com/t/b3374bb0337a/wordpress-index-page-is-giving-404.html