I'm adding Pivot table source update comment in case others have the same problem.
I created a pivot table whose source data changed because I added rows to the source. When I clicked on the Change Source Button to extend the pivot table source to the additional rows, the Change PivotTable Source window popped up, but Excel did not return to the source data tab with the current row and columns marked. Instead, it just remained on the Pivot table tab. When I manually entered the new table source rows and columns on the Change PivotTable Source form and clicked ok, Excel erased my Pivot table.
Excel is supposed to take you to the source table tab with the current selection marked, where you can either mark the new source rows and columns with your mouse or manually enter the rows and columns. When you press Ok on the Change PivotTable Source pop-up, Excel is supposed to update your Pivot table with information from the new source rows and columns.
Navigate to the Excel Options’ Data tab and uncheck “Prefer the Excel Data Model when creating PivotTables, QueryTables and Data Conversions.” If you need to leave this option checked, be careful to uncheck Add this data to the Data Model on the Create PivotTable pop-up when creating a new Pivot table.