I have developed a website for a client using Umbraco 7.4.3 and the website has filled with content and ready to go live. My client deploy this website under a subfolder of their own main domain, likes domain.com/newsite
with virtual directory method on IIS. notes: main site is also umbraco.
When the new site accessed, it always redirected to /install just like the first-time installer wizard when we just deploy original Umbraco, though it keeps loading forever and not showing anything. I already found similar problem (deploy as subfolder/virtual directory) and following solution provided, but didn't find one exactly like my case. When I tried on my local machine (other than development one), I couldn't reproduce the problem.
I wonder what setting or configuration did Umbraco used to tell it to run installer? all *.config and database used exactly the same except connectionString.