Pivot tables not updating after adding a slicer

Hi,

I have created a dashboard using a table from an external data source and pivot tables which works fine, however, when I add a slicer to allow me to select the data by month the pivot tables don't refresh unless I unselect and then reselect the months on the slicer.

Any help would be greatly appreciated.

The source data updates when the dashboard file is opened, no data is deleted, the updates are either data rows added for new projects or dates for milestones have been added to existing rows. The data table from the external source and all pivot tables are set to update on file opening. The dashboard will update on the file opening and works as expected without the slicer present.