Ryan,
Stripline added to second axisX is not displayed as second axisX doesn’t have any range (minimum and maximum of the axis). In case of multiple axes, axis will have it’s range when either dataSeries is attached to the axis or range is defined. You can set range of second axisX to be same as first axisX using get and set methods as shown in this updated JSFiddle.
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Vishwas R
Team CanvasJS