PivotTables are not updated each time a change occurs in their source data. To update a table, select any cell in the table and choose Data, Refresh External Data, or click the red exclamation point on the PivotTable toolbar.
If you want Excel to refresh your PivotTable every time you open the workbook in which it resides, choose PivotTable, Table Options. (The PivotTable menu is on the PivotTable toolbar.) Then select the Refresh On Open check box in the PivotTable Options dialog box. If you want to prevent Excel from updating the table each time you open the workbook (for example, if the table is based on a time-consuming query of external data), be sure this check box is cleared.