Do not use the PASSWORD but the encryption key.
With a new NS8 and backup/restore, I had the same problem until I used the key instead of the password. NS8 - Backup and restore (Windows file share).
Also, the checkbox “Replace” should be active for the restoration of a single app; without it, the restoration will add the restored app with a new number, alongside the original one…
I had 3 apps backed up. I restored, with Replace, the first without any problem. The restoration of the LDAP was impossible. I will investigate today.
Michel-André