“Unable to shutdown system “Error - You don't have permission to shut-down this computer

Possible cause: 

This could be caused by ‘User Account Control’.

There are distinct policies governing ‘UAC’ behavior, one for built-in Administrator account while another is for all other administrative users.

By default, built-in Administrator account is not affected by ‘UAC’, while all other administrative users are; thus, it's possible for an administrative user (different from the built-it Administrator) to not get administrative rights, even if it's a member of Administrator’s group.

Steps to resolve:

         1. Press “Windows+R” together and it will open run window.

         2. Type “gpedit.msc” and click ‘OK’

3. Navigate below settings.

Computer Configuration --> Windows Settings --> Security Settings --> Local Policies --> Security Options

         4. In right side pane, find out below option.

User Account Control: Run all administrators in Admin Approval Mode (select ‘Enable’ & click ‘OK’ to apply changes)

*In order to implement change, system restart is mandatory.

*To restart the system Press “windows+r” together and type “shutdown -r”.

 *Seqrite at this point have not confirmed the exact cause leading to this behavior. For the reported cases, following the above steps should help resolving the issue.