I don’t know if you’re familiar with bbpress, it’s the forum cousin of wordpress and can integrate nicely into the wordpress database to allow users to be shared across the two installs. So, on my North Carolina Genealogy site and my South Carolina Genealogy site I have bbpress forums installed. The catch is I wanted everything accessible through forums.domain.tld for each one. This worked with a simple config.php edit on the North Carolina site, but not the South Carolina Genealogy Forum. I kept getting 404 errors. So, I spent a couple hours chasing .htaccess Nothing I tried worked, I copied working files from one to the other, I looked at httpd.conf settings.