There are 3 main reasons why this would occur:
1. The backup did not include the option in the 'Backup Options Set' to "Backup ACLs." So, in this scenario, there would be no ACLs to restore.
2. The option to "Restore ACLs" in 'Restore Options' was not checked, thus, the ACLs will also not be restored.
3. Provided that both the above options were in fact used however, the 3rd reason why is how the restore is being done. If the DAR restore is done at the subvolume level, the parent level permissions are not restored.
To ensure that ACLs are restored, the above options must be applied. For the 3rd reason in that list, the only way to restore the ACLs in this scenario is to select the root volume of the data you are selecting to restore. This is a limitation at the NDMP level and not with the NDMP Plugin itself. This is solely in the DAR scenario. Non-DAR restores do not have this limitation.