Roundcube login page does not show CSS/JS elements and pictures if domain is assigned to the newly added IP address.
From the original IP address Roundcube works fine.
/etc/nginx/plesk.conf.d/webmail.confis not regenerated after adding a new IP address.
Bug #PPPM-3443. It is fixed in Plesk 12.5 MU #10 and Plesk Onyx.
Install the latest microupdates or upgrade to the latest Plesk version.