Active and Inactive customers

First of all .date is only need when you have a timestamp. Second use a date table.  3 formulas, I am giving. Third one should work

//1
CALCULATE(
      DISTINCTCOUNT( TableA[ID] )   ),
    DATESINPERIOD( TableA[DATE], MAX( TableA[DATE] ), -6, MONTH )
)
//2

CALCULATE(
      DISTINCTCOUNT( TableA[ID] )   ),
    DATESINPERIOD( DATE[DATE], MAX( DATE[DATE] ), -6, MONTH )
)
//3
sumx(summarize(calculatetable(TableA,DATESINPERIOD( DATE[DATE], MAX( DATE[DATE] ), -6, MONTH )),
TableA[ID] , "_active",distinctcount(TableA[ID])),_active)

To get the best of the time intelligence function. Make sure you have a date calendar and it has been marked as the date in model view. Also, join it with the date column of your fact/s.

Refer
https://radacad.com/creating-calendar-table-in-power-bi-using-dax-functions
https://www.archerpoint.com/blog/Posts/creating-date-table-power-bi

https://www.sqlbi.com/articles/creating-a-simple-date-table-in-dax/

Appreciate your Kudos. In case, this is the solution you are looking for, mark it as the Solution. In case it does not help, please provide additional information and mark me with @
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