@lindsay10c,
Based on the sample project shared by you the SQL query used seems to have some issues. Comparing timestamp properly should work fine in your case, i.e. SELECT timestamp, count FROM skelCount WHERE timestamp >= TIMESTAMP(DATE_SUB(NOW(), INTERVAL 1 day))
should work fine in this scenario. Please take a look at this StackOverflow link for more information on fetching data n days ago.
Also, kindly take a look at the updated project. Below is the screenshot of the chart when its run in local-server.

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Indranil Deo
Team CanvasJS