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I am sorry to hear that you cannot make the knock pattern work. The unfortunate aspect of it would be, that you may have to hard reset your LG Pad, in order to regain access to it.
If you hard reset it, that would mean losing all the data individual to you that is stored on it. If that data has not been backed up already, you would do well to first connect your LG Pad to your computer, with a USB cable, and see if you can get files individual and valuable to you off of it, and copied onto the computer.
To hard reset the LG Pad UK410:
From a power-Off condition, do the following steps
Press and hold the Power buton and the Volume Down button and the Home button, all three at once.
Keep holding them until the LG logo appears, then release all three buttons.