how to create sub group in data table

[jpaulphan]

I would like to know how to add the "year" to my graph data table. Table shows months but not the year for some reason.
See picture attached.

Thanks a lot

[JeteMc]

Hello jpaulphan and Welcome to Excel Forum.
My suspicion is that this is related to using an online version because years and months can be displayed in a data table using a desktop version.
In the attached file there is a chart with a data table for a regular table and for a pivot table.
It may also be related to using an online version that causes the months from 2023 to not display in the data table shown in the screenshot.
Sorry not to be of more help.