Use CONCATENATEX for Debugging

 3 Month Sales Rolling Average (ConcatenateX) =

VAR EndDate = LASTDATE('Date'[Date])

 

RETURN

CALCULATE(

CONCATENATEX(

VALUES('Date'[MonthNumberOfYear]),

'Date'[MonthNumberOfYear], ", ", 'Date'[MonthNumberOfYear]),

DATESINPERIOD(

'Date'[Date],

EndDate,

-3,

MONTH))