@khurram-khan,
There have been bug fixes and improvements with regards to indexLabels in the previous versions. You might be using an older version of CanvasJS, which might be the reason you are facing this issue. Kindly download the latest version of CanvasJS Charts from our download page, update it in your application, and let us know if the issue still persists.
Considering this as duplicate of Issue in chart indexLabel, and hence closing the same.
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Ananya Deka
Team CanvasJS