Managed backup restore not working

Cannot restore from Managed backup, member needs to restore to the the old backup, and would prefer faster ways.

Tried the restore button in the plugin dashboard page, but getting the following error:

For a faster solution, member tried by running snapshot installer plugin, but not able to establish connect with the DB, and is getting the following error:
Warning: ZipArchive::extractTo(/tmp/si_test/snapshot_manifest.txt): failed to open stream: Permission denied in /home/nekuda4admin/public_html/snapshot-installer.php on line 802

DB details, and cPanel access has been provided via chat. Support access enabled.