‘www’ prefix not working

If you didn’t add the ‘www’ prefix at the time of setting up the domain, even adding it back in later does not seem to work.

Solution:
To work around this problem, firstly – turn on the ‘www’ prefix again within the Plesk control panel.

Go to Plesk CP > Domains > yourdomain.xxx > 'Domain Administration' drop-down menu > Rename domain. It will force IIS to configure www.yourdomain.com hostheader for your domain.

Also, make sure your www.yourdomain.com resolves to the same IP adress as yourdomain.com.