Posting a sample sheet would have helped ( no pics please). We now can only try guessing. As for your dates, the format might be correct but are they real dates? YOu van verify this if the dates are right-aligned in the cell when no manual alignment is applied

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Thanks Pecoflyer

Yes - they are dates. When I Clear>Clear Formats, I get a numerical value

I tried creating a new Pivot Table from the existing Data Table and I only have an option for Date. I do not get an option for Date (Month). I'm assuming this is the issue, but I have no idea how to fix it.

UPDATE:
When I created the new Pivot Table and actually selected the Date as one of the rows, miraculously, the Date (Month) option was added to the Pivot Table Fields selection pane.

I am now able to Pivot the data for the new month just added.

I've been doing this for years and never had this issue before, so don't know what happened.

Thanks for the support Pecoflyer