Hi Keocera,
It's been a while since I set the levels on ours so I just went out and did it to verify the procedures. Both worked as advertised. First, make sure the water pump is ON. You have to hold both buttons down at the same time for about 5 or 6 seconds, at which time the bowl will begin to fill with water. When it gets to the desired level, release the buttons.
If yours isn't working, the only things I can think of that could be causing the problem would be, (A) - your water pump isn't ON or (B) - you may not be holding the buttons down long enough. Let me know if this helps.
Kev