Hi- we have Milgard windows, and the one in our kitchen seems to be locked. Normally you press the lever in the picture to the right and pull the window to the left. This window suddenly will not move to the left to open it no matter what. It seems to be stuck at the bottom. I've pulled it left with significant force while pressing the lock... nothing.. I tried sticking a knife in the small slot to operate the mechanism in there before trying to open it, but it's still stuck. Also tried moving the lock up and down the window frame but it makes no difference. Any thoughts/advice?