@armangh,
Calling render method after mounting (testMounted value changes to true) should work fine in this case.
If you are still facing the issue, kindly create a sample project reproducing the issue and share it with us over Google-Drive or Onedrive along with the sample data so that we can look into the code, run it locally to understand the scenario better and help you resolve.
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Manoj Mohan
Team CanvasJS
