Hi Ben,
I restarted Naviserver but the redirection is broken. It still doesn't work. The subdomain is present in the address bar, but the page, which displays is Mainsite default page ( i.e. acs-subsite/www/index).
I'm a using a proxy in front of Naviserver, and I wonder if NGINX could affect it somehow.
How could I track this error down to its root cause?
In parallel, It seems Host-Node map feature isn't completely developed. I found this old thread
https://openacs.org/forums/message-view?message_id=187226#msg_494834