countrows with multiple filter values selected

Hi aragu !

Let's try do it step-by-step.

Capture the Selected Test Passes:
Begin by capturing the values of Name_Testpass that have been selected in the slicer.
VAR SelectedTestpasses = VALUES('Platform_time'[Name_Testpass])

Filter the Data:
Filter the entire 'Platform_time' table to only include rows where:
The P90_pass column has a value of "FAIL".
The Name_Testpass column's value is among the selected test passes.
VAR FilteredData =
FILTER(
ALL('Platform_time'),
'Platform_time'[P90_pass] = "FAIL" &&
'Platform_time'[Name_Testpass] IN SelectedTestpasses
)

Count Unique Metrics:
From the filtered data, summarize by the Name_Metric column to get unique metrics. Then, count the number of rows in this summarized table, which will give the count of unique metrics with a "FAIL" value for the selected test passes.
COUNTROWS(
SUMMARIZE(
FilteredData,
'Platform_time'[Name_Metric]
)
)

Final Formula:

Combining the above steps, the complete DAX formula is:

Fail_Count =
VAR SelectedTestpasses = VALUES('Platform_time'[Name_Testpass])
VAR FilteredData =
FILTER(
    ALL('Platform_time'),
    'Platform_time'[P90_pass] = "FAIL" &&
    'Platform_time'[Name_Testpass] IN SelectedTestpasses
)
RETURN
COUNTROWS(
    SUMMARIZE(
        FilteredData,
        'Platform_time'[Name_Metric]
    )
)

This formula will provide the desired count of unique Name_Metric values where P90_pass is "FAIL" for the selected Name_Testpass values.

Perhaps my colleagues will suggest a different solution @tamerj1 @annonymous1999  @OwenAuger