Google-Line-Chart on hover tool-tip not showing value

[AkashJain]

I have used Google Line Charts in Angular2 in typescript version, When I draw the line chart, Chart is looking good but when I hover over the line chart to see what is exact value at that point, I can't see any value in tool-tip and I don't understand what can be the problem if the value has been drawn in chart but aren't showing up in tool-tip. I have attached a screenshot for the reference. Kindly help. Thanks in advance.