As far as I understand it, if your backup file is larger than 2Gb it will not restore properly (or not at all). It's a limitation of smb, tar and even the browser you use.
You need to make a new backup less than 2Gb (split if neccessary by backup2ws contrib), and start again. This subject has been extensively covered in the forums, search on backup and backup2ws and go back a year or two.