Introduced in build 8.4
Sets or returns whether Microsoft Excel will automatically refresh a PivotTable and the PivotTable cache when Excel opens the document.
false by default.
When creating or modifying a PivotTable with ExcelWriter, make sure to set this property to see the changes. If this property is not set in code or in a template, the PivotTable will not reflect changes made with ExcelWriter code.
RefreshOnOpen is the same as going to PivotTable Options > Data and checking or unchecking Refresh data when opening the file.