Not able to group in second pivot table (new sheet)

Hello,

I want to do several pivot charts in one workbook in different sheets. I was able to succesfully group data (these were the balances in bank accounts) using the "Group" Button on the ribbon (in the Pivot Table section) once.

Now, in a new sheet, I want to group the same original data but different indicators (estimated salary of customers). Now, when I go to the "Group" button, the third option (which I need) "group this field" (or something like that, I am using the German version) is grey and I can't use it.

I suspected it could be the pivot table cache and I told Excel via the Pivot table wizard that I don't want to use the pivot data memory (clicked 'no' on the third option). Still, I can't group the data in the second pivot table of the workbook.

Any suggestions are highly welcome! Thanks!

There are instructions at the top of the page on how to post a sample sheet.Thanks

It is working now, there was a different format in two of the cells, that's why it wasn't working.

I wanted to delete this post but didn't find a way to do so, sorry!