Lost customers no purchase more than 6 months

[EV]

I tried all possible solutions and tried techniques suggeste, but still cant ge through this.

All im tyring to do is show the lost customer sales from previous year, who didnt purchase for 6 months from selected month. Group by customer and Item.

I created 3 measures, All works except the total. It seems to consider total onlly for current year or not at all.

Last period sales = 

CALCULATE( SUM(Sales[REVENUE_USD_FxAdj]),DATESINPERIOD('Calendar'[Date],LASTDATE('Calendar'[Date]),-7,MONTH)
)

prior year sales =

CALCULATE (
    -Sales[SALES REVENUE_PY_FxAdj],
    DATEADD ( 'Calendar'[Date], -1, YEAR )
)

lost customer sales = If last period sales is less than or equal to 0 or blank, return the prior year sales for that month in negative.

IF(OR(ISBLANK([Last Period Sales]),[Last Period Sales]<=0), [Prior Year Sales],BLANK()) 

I am seeing right values for the lost customer sales but total is blank.

I tried all possible SUMX, SUMMARIZE, still it doesnt work.

At the end I want to be able to see the total for each month in the below table

Please can someone help me.

 @OwenAuger  @MFelix  @Zubair_Muhammad Please can you help