All computers are already activated. The key is embedded in the motherboard and cannot be retrieved by an app. There is no need to reactivate. Go to the Desktop, right click on the Start button and select System to see the activation status. Did you purchase the computer from Dell? Did you make any changes to the computer? 
so i bought a new Dell Inspiron 3521 laptop with windows 8.1 and i am not able to activate it!i tried the 'Activate Online' option which was of no use and i cant find the key anywhere! (i did not receive it)and also i have used an app to locate my key and i tried entering it but that also dint work!i am spending hours on this now!please help!
Windows 8.1 Activation!