Adding chart to track value over time fails

Hi,
Attached screenshot of sheet with formulas shown. I’ve had issues with attempting to plot cells D7 or E21. Anytime the Xaxis type is set to Time, it exhibits the issue.
BTW: this is a simplified sheet that is a subset of the other sheet where I originally encountered the issue and I’m not experiencing the issue when the chart is added now; only when the chart Xaxis type is changed to Time. I may be doing this wrong so thank you very much your attention!