Verified answer

You need to get the encryption credentials from the previous owner. We use this exact product, but from an Enterprise level management console. The idea is the same - get the password, and if you want to keep the encryption, you should change the pass key/phrase. I would decrypt the computer first with the previous owner's pass key, then uninstall and reinstall the encryption agent (if you can, but it may not be that necessary). Then re-encrypt with your settings. The computer does need to restart once before the encryption can begin for the first time, so that will be normal.