KB ID 0001521
If you attempt to restore items from a backup of a server where the data was stored on a deduplicated volume, you may see the following error;
Copying data from deduplicated volumes requires that the console is installed on Windows Server 2012 R2 or later with the data duplication feature enabled.
Restoring files from deduplicated volumes requires that the mount server associated with the source backup repository uses Windows Server 2012 R2 or later with data deduplication feature enabled.
This tells me two things, firstly no one at Veeam can use a comma, and secondly we are missing a Windows feature.
Normally if you see posts for this, it will tell you to install the deduplication on the Veeam server, (because that fixed their problem). That worked because the mount server and the Veeam Backup and Replication management server were the same server. However if you are remote managing Veeam, then the mount server is the server you are running backup and replication management on. You need to bear this in mind, if you are managing Veeam from an OS that does not support Deduplication, then you may need to remote onto another server to perform the restore.
Open a PowerShell session, and execute the following commands; (That last one will reboot!)
Import-Module ServerManager Add-WindowsFeature -name FS-Data-Deduplication Restart-Computer
Retry the restore;