Hi Ingmar
There seems change in original problem reported. I was making sites online and offline, clearing browser cache etc. Some how, not sure how, I am unable to reproduce exact same issue. but noticed a different issue that I am able to reproduce.
I have only one user in the system (i.e super user). I don’t have any frontend login. So it is just a public access (or anonymous) to the front end.
Openned 2 different browsers
a. Google Chrome (GC): For admin configuration and checking
b. Internet Explorer(IE): for Public acess
GC:
a. tab1:Logged in as super admin through default_site admin page. set Default_site status offline and selected the additional site (SiteB) from the sites menu and set status of it to offline.
b. tab2 - acessed default_site front end - able to see the website
c. tab3 - accessed second site front end - site offline message
Checked in IE: (results as expected)
a. tab1: default_site - site offline message
b. tab2: second site - site offline message
Simply, if the site is offline for the second site, even though you have logged in as super admin, unable to see the front end website.