BuddyPress.org

Okay! I took a tip from https://buddypress.org/forums/topic/can-i-run-non-bp-theme-on-tld-and-bp-theme-on-subdomain-all-on-same-wpmu-install

Check this, I’m NOT using Blog #1 as my main blog (long story).

I put this in my wp-config.php and it’s working!

/** Buddy Press **/

define( 'BP_ROOT_BLOG', 3 );