During upgrade to a newer version of Veeam Backup & Replication, the following error occurs:
The version of Veeam Backup & Replication does not comply with the license version.
Make sure that you are providing a license file for version 6, not for an earlier version. To verify the version of your license file, open the license in the Notepad and check the "Version=" line at the bottom.
To find out how to obtain a license for you version of Veeam Backup & Replication, follow KB1370.