Where do you have you vPower NFS configured? That might be a permission issue - please check if vPowerNFS and Veeam Backup services have enough permissions on the vPower folder.
Also, please check if there are any orphaned instances of the same NFS on you ESXi - if any then delete them, do a rescan and try restoring again.
P.S. This thread
contains some information on this issue, please check.