Hello,
Thanks for querying in this forum.
According to your description, it seems like you want to create a pivot table for the data in a Excel file which is related to a form's results, the Excel file will get new data update and you want the pivot table also gets update.
May I know if my understanding of the scenario is consistent with yours?
If yes, we'd like to let you know that if you create a form from Microsoft Forms for the web, the related Excel file is offline and won't get continues update data.
Only when you create a form from OneDrive for business(click New > Forms for Excel) or Excel for the web( Insert tab>Forms>New form), your Excel file is automatically stored in OneDrive for work or school and contains a live data connection to your form. Any new response data in your form will be reflected in your workbook.
Here are articles for your reference:
Create a form with Microsoft Forms
Check and share your form results (microsoft.com)
So we suggest you create a form from OneDrive for business or Excel for the web. Then you can find form results Excel workbook by clicking Open in Excel from Responses page, it will open the file in your OneDrive for business. Then you can create pivot table by using the data in the Excel file.
Per our test, when we get new responses in the form, the Excel file in OneDrive will get updated data, and we can refresh the pivot table to get updated data.
You can also manually refresh the Excel file by click Refresh from Data tab.
Hope above can help you.
And if our understanding of the scenario is not consistent with yours, feel free to point it out.
Thanks for your patience and understanding. Hope you are keeping safe and well!
Best Regards,
Tina