Error with installing FortiClient on Mac OS 15.6.1

Hi,
I am trying to install FortiClient 7.4 onto my Mac (OS 15.6.1) for the very first time.
After downloading the dmg file and double clicking on it, the Installer window pops up.
After double clicking on that installer to download the app, I keep getting an error saying, 

''Can't connect to update server''
How can I fix it ? I tried updating software, uninstalling and reinstalling the dmg file but it just doesn't proceed.
Any help is appreciated 
Thanks a lot !