Since you are running release 5.x, please use archiving in the RRC. You will need to (in Archive->Media) scan the media, mount it, import it and then go to the Archive->Status to perform the restore.
Regarding the share, it could be a couple of things. If you want to continue the restore in this way, I would start by running the following at the Terminal:
chown -R nobody:nobody /backups/ArchiveRestore
service smb restart
If you are still having an issue with the archive restore, please contact Unitrends Support Center at (888) 374-6124 and reference this forum post. Thank you.