Till, please let me know how can we reinstall ispconfig and test with a new installation....
There is no need to reinstall your system.
The ssl vhost is not created when there is a problem with the ssl certificate e.g. because openssl could not create the cert due to special chars entered in the ssl cert detail fields. Ensure that the ssl checkbox is enabled in the website settings and that you selected a Ip address in the website settings. Go o the ssl tab of the site and select delete as action to remove the broken ssl cert and click on save. Then neter the correct ssl cert details, choose create as action and click on save and wait 1-2 minutes.
The detailed instructions on how to create a ssl certificate aredescribed in the manual as well.