AutoLock automatically locks the BlackBerry keyboard after the backlight turns off, optionally waiting a configurable delay after the backlight shuts before locking the keys.
To enable/disable or set the delay, go to Options->AutoLock.
Link OTA :
b. Purchase License
è There is a known issue with the locking feature of OS version 184.108.40.2064 and later. This application will not fix the error with locking on that OS build. The device will not lock without a passcode set in “options-security options”