@RiyazBasha. Web Report is a web server with the following directory (drive letter might be different) as the root directory.
C:\Program Files (x86)\BigFix Enterprise\BES Server\wwwrootbes\
With a proper installation, we should see a directory like the following
C:\Program Files (x86)\BigFix Enterprise\BES Server\wwwrootbes\ext-3.2.0
So a proper test URL should be:
http(s)://your_web_reports_server:port/ext-3.2.0/ext-all.js