Remote lock question - Newbie

Hi

 

This is my first time using this product.

I have a Samsung Note 2 and i have installed the "Norton Security and Antivirus" via Google Play store

 

My question is...

 

1) when i try to sent a command  from my other phone to test...using "lock Password999" the lock command via sms. It said.. "Remote code  is incorrect" on the Activity Log.

 

What am i missing?

 

Please advice.

 

TIA