Which version of Office are you using? Such as Office 2016, Microsoft 365 apps.
Does your Pivot Table have any Filters fields?
If yes, it is recommended to tick the boxes of all items to show all data. Besides, you may right click the "All" cell > Field Settings > Tick the box of "Include new items in manual filter".
Besides, I suggest you refer to this article to change the source data for a PivotTable to check this issue.
Any misunderstandings and updates, please let me know.
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