I am having problem downloading application on Mac app store, when I try to login and start downloading the application, it will say "Your device cannot be verified"

Question

I am having problem downloading application on Mac app store, when I try to login and start downloading the application, it will say "Your device cannot be verified"

Answer 1

Back up all data before proceeding.
Step 1
Triple-click anywhere in the line below on this page to select it:
/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist
Right-click or control-click the line and select
          Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.* A folder should open with an item selected. Move the selected item to the Trash. You may be prompted for your administrator login password. Restart the computer and test.
*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination  command-C. In the Finder, select
          Go ▹ Go to Folder...
from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.
Log out, log back in, and test. If there's no improvement, continue.
Step 2
Reset your computer’s PRAM.