We are using Kentico 12SP (hotfix38). The offline mode doesn't work like it should in my opinion.
I followed the instructions from :
Switching sites to off-line mode
I see the message:
The site is currently off-line. To enable site visitors to access the site, bring the site on-line.
and the site is still alive and well, when it should be showing the offline page.
The database SELECT [SiteIsOffline] FROM [KenticoCMS].[dbo].[CMS_Site] is true.
What is missing that the site doesn't go offline.
I recycled IIS pool, reset IIS. The site is still showing like it was live.
The only way I could make it go offline is the app_offline.htm