Note: This bug only affects version Plesk 10.3.1
Unknown key propery: concerto
references to common_func.php3 and key_update.php
(see screenshots below)
If you see this error when trying to retrieve a license key directly from the plesk panel, upload the common_func.php3 patch to the customers container (/vz/root/<VEID>/usr/local/psa/admin/plib/common_func.php3)
[Note: If the container is not mounted, then you may need to copy to the /vz/private path]
If you don't feel like trusting the patch from my site, see the external link to parallels forums at the bottom of this article.
Then try to click the "Retrieve Keys" link again in the Plesk Panel: