You have removed the vertical axis in your Reporting Services chart and you can’t find where to restore it. Restore a hidden vertical axis in a Reporting Services Chart as follows :
1. Select the Chart
2. Go to the Properties pane
3. Select the Ellipses (…) beside the ChartAreas Collection
4. Select the Ellipses (…) beside the VerticalAxis Collection
5. Select the axis whether it be the Primary or Secondary axis, then set the property for Visible to True.
6. Click OK