Mine will lock and unlock the way it is supposed too.
When you tap the power button.
You will see:
Unlocked Lock -> Locked Lock
+ >>> >|| >>> []
Swipe directly across or press the three keys quickly in sequence...
If you do it correctly, the top icon will change to a Locked Lock only and the keyboard will be disabled.
If you do not see the Locked Lock by itself, your attempt did not work. Try again...
To Unlock:
Press the power button again.
You will see:
Locked Lock -> Unlocked Lock
+ >>> >|| >>> []
Swipe again or press the three keys quickly in sequence...
This time the top icon will change to an Unlocked Lock only and the keyboard will be enabled.
I still have the shipping protector on my screen until a proper screen protector arrives, so I have a hard time swiping to get the lock / unlock to function. I get better luck by pressing the keys quickly in sequence.
