Upgrade key not imported

I got the license key, the license manager reports that the key (upgrade to 2.1) has been imported successfully. However the key does not appear in the list of regsitered keys and VPUML shuts down.

By using the upgrade key, you need to import the 2.0 key first. Please make sure that you have 2.0 key in the key manager, than import the upgrade key. Thank you.

Best Regards,

2.0 key is imported and listed in license manager window. Still the upgrade key cannot be imported.