Can't get Latch & Keeper to Line Up
Don
Hopefully I can help! Sounds like your window main frame could be installed improperly. Perhaps the cut out for the window was not made tall enough making the sashes too tight to lock. You ought to check to see if your sashes were "glazed" out of square. Also check the sill bubble at the bottom of the lower sash to see if you use a smaller sill bubble, and also check the top rail to see if you can replace that bubble. Maybe that will give you just enough room to lock the sashes. You also could try filing down the hook on the sweep latch. That too might give you a little more play.
One more trick might be to cut off the part that hangs down in the keeper so that there is just a hole in the keeper. Let us know if one of these options works for you.