Method 1:
Solution through Group Policy:
Open gpedit.msc (Group Policy Editor)
Browse to Computer Configuration->Windows Settings->Security Settings->Local Policies->Security Options
Enable “User Account Control: Admin Approval Mode for the Built-in Administrator account”,
Restart workstation (Restart the computer)

Method 2:
Solution through registry:
Open regedit (Search from start menu)
Navigate to: HKEY_LOCAL_MACHINE-SOFTWARE-Microsoft-Windows-CurrentVersion-Policies-System
Make sure the value "EnableLUA" is set to 1
Restart workstation (Restart the computer)