Excel Chart Trend line Help

Hi There, While going through Excel charts, A thought of Adding a trendline hit my mind and so I did try adding one by following all the steps mentioned on the below link;
https://support.microsoft.com/en-us/office/create-a-chart-from-start-to-finish-0baf399e-dd61-4e18-8a73-b3fd5d5680c2?wt.mc_id=otc_excel ;
But unfortunately I faced some new message (Something Not mentioned on that link)

For reference view the below image;