Executing the following command resolved the issue :
/usr/local/cpanel/bin/register_appconfig /usr/local/cpanel/whostmgr/docroot/cgi/softaculous/softaculous_whostmgr.conf
We do execute this command while installing Softaculous but we are not sure why it failed to execute during installation.
There are some strange things on your server like the Softaculous folder is protected in some way that we are unable to delete it for re-installation. I believe there is something wrong with your cPanel installation that could be the reason why some cPanel commands failed to execute during Softaculous installation.