Legend issue with Pivot Charts

Hi

I have created an Excel interactive dashboards using pivot charts and slicer for the period Fen and Mar 2022
On the attached, the first image shows both Feb and Mar data with the months in the legend. When I select Feb in the slicer only Feb data is shown along with only Feb in the legend.
However when I select Mar in the slicer, while the graph displays Mar data, where Mar 22 should show in the legend, its been replaced by the items listed in the X axis. I have tried deleting and recreating the graph however the issue remains

Can you please explain the process, I have googled it and the results don't relate to my issue