@dpanscik,
You can get your extra data passed to datapoints using chart object as shown below
var pageName = chart.options.data[0].dataPoints[0].extraData[0].value
var alertMessage = chart.options.data[0].dataPoints[0].extraData[1].value
If you are still facing issue, kindly create a sample project reproducing the issue you are facing and share it with us over Google-Drive or Onedrive along with sample data so that we can look into your code, run it locally at our end to understand the scenario better and help you out?
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Manoj Mohan
Team CanvasJS