GET PIVOT Data when grouped by Month and year

[kizzie37]

Hi Have a pvito table that I have grouped by:

Year
Month
and then by "Leave Type"

If i use =GETPIVOTDATA("Count of Worker",PIVOT!$AB$6,"Last Day of Work",K23 (K23 being Sep)

I get the results for Sep across all the years, I cannot figure out the formula to give me Sep just for 2021, I just get a "Ref#" error.

Can anyone help?