You may get an error during the upgrade of Veeam Backup & Recovery to version 8, stating that the vPower NFS service is unable to start. Alternatively, when updating the individual components, you may also get a similar error (such as: "Error 1920.Service Veeam vPower NFS Service (VeeamNFSSvc) failed to start. Verify that you have sufficient privileges to start system services.").
There are several reasons possible for this, but the most likely one is a wrong NFS Datastore path specified in the registry, usually because the drive that the datastore is pointing to, is no longer present.
Another reason could be that your server has the "NFS sharing" feature installed, in which case the TCP/UDP-ports are already in use.
You can verify the exact reason by looking at the log at %PROGRAMDATA%\Veeam\Svc.VeeamNFS.log. In the log (at the bottom), you will find a clear error message, stating exactly what's wrong.
If the path is wrong, this can easily be fixed through the registry:
If you have the "NFS sharing" feature installed, the only way to resolve this issue, is to remove the feature from the server you're running Veeam on.