@larry,
The behavior is designed such that zooming is limited upto a certain region, so that user doesn’t end up zooming into a blank-region (region with no dataPoints). To zoom into a certain region, there should be a minimum of 3-4 dataPoints over the axis.
In your case, the zoom doesn’t work as there are less than 3-4 dataPoints with different values over the axisY.
We will reconsider this behavior for future releases.
—-
Manoj Mohan
Team CanvasJS