After creating a pivot table, you need to change the data source if you have made changes to the data. Please see below for details:
Step 1: Click any cell in the Pivot Table;
Step 2: Click the "Analyze" tab from the Ribbon (Note: please click "Options" if Excel 2010), then click "Change Data Source" command in the "Data" section;
Step 3: This will guide you back to the data source and you need to select the data range to include all data;
Step 4: The pivot table will also change based on the new data range.