Ran into this Veeam error today when demonstrating Veeams Explorer for SharePoint to a customer.
The customer was using a supported version of SharePoint and Veeam was configured to use a licensed version SQL 2014. After checking over the backup job settings and ensuring no errors or warnings were being thrown I hit the Veeam forums. Fortunately, someone else had seen the same problem which you can find here.
“The Application-aware logic uses NetBIOS names to locate corresponding SQL servers during backup and in some cases (where SQL server for the site collection is specified using IP address or SQL Server alias, for example), Veeam B&R still does not have the required information, even provided that application-aware backup was successful. If this is your case (I believe support will be able to verify that), you can configure SQL server mapping manually via the registry, as far as I know, there’s an ability to do that.”