For export scenarios and for restoring to the state before a selected transaction, Veeam Explorer for Microsoft SQL Server uses a staging server. This staging server must support and be able to read the encrypted database. For it to read the encrypted database, you must first restore the certificate protecting the Database Encryption Key. See System Requirements for Veeam Explorer for Microsoft SQL Server for more information on the staging server.
Note: Transparent Data Encryption requires the Enterprise edition of Microsoft SQL Server; this also applies to the staging server.
If you are not exporting or restoring to a specific transaction, but you are restoring to a different SQL Server instance than the one the database was backed up from, the error means that the restore target SQL Server is unable to read the encrypted database. You must first restore the certificate to the SQL Server before restoring the database.