Unfortunately, the only way to get the key is through SAP.
If you have an account on their portal, you'll see the various servers that have been licensed for the different products. One of these should be for the BO server (formerly Crystal); and you would be able to use that to get the relevant details.
If you don't have an account, you should be able to get one, probably via the re-seller that sold you the copy of Crystal.
Oct 09, 2014 SAP Note 1566573 (Most common SAP BusinessObjects license key related) also contains additional information on common errors. Temporary license keys. If there are any errors creating a permanent license key, temporary BusinessObjects license keys are available in the SAP.
Unfortunately, I no longer have access to the support portal, otherwise I would provide a link to get you started.