Hi @Maria, Sum() function needs a measure by which to sum the result and Filter() function needs a set from which to filter the results.
Try this formula:
Sum(
--go through all test cases
Filter(
Descendants([TM4J Test Case].CurrentMember,[TM4J Test Case].[Test Case]),
--filter by actual
[Measures].[TM4J Test Case Archived?] = 'Actual'),
--sum by measure
[Measures].[TM4J Test Cases with Test Cycles]
)