Cannot calculate rolling 6 week average

[stw]

Hello all.

I am fairly new to Power BI, but I have managed some basic things already.
My problem at the moment is as follows:
I am using the following tables:
date table (date, iso_week, year, month, month_name)
orders (order_number, order_date, number_produced, SAP_number)
repairs (order_number, SAP_number, repair_id, repair_date and some more columns)
and a table with dax calculations:
dax (repairs[distinctcount with repair_id], produced_items[sum of number_produced], repair_quote[repairs/produced_items])
So far this works, I can display the number of produced items per iso_week and also show the RQ for each of these weeks, and I can also filter for different SAP numbers and years. Basic, I know.
Now I want to calculate a rolling 6 week average of the calculated RQ value - and nothing I've found online so far works.
Because I have my own date table I cannot use the quick measure. 
I don't know where to look.
What I have so far is this:

Produced 6W = 
CALCULATE(
    AVERAGE('DAX'[RQ]),
DATESINPERIOD(Dim_Datum[Date],LASTDATE(Dim_Datum[Date]),-42, DAY)
)

 But it does not show me any values for the weeks of any year.

Help would be much appreciated! 

[stw]

I've just watched another tutorial about creating rolling average measures.
Can it be the reason mine is not working is that my measure "RQ" has somehow no connection to a date so I can't use the average functions with dates because I am calculating the RQ value for each individual week?
Maybe I should step back and ask: how should I arrange my tables and measures so I can calculate a RQ for each order  and then show for each week or month the number of orders, the RQ and the 6wAVRG RQ?

[stw]

Quick update:
I changed the formula as follows:

Produced 6W = 
CALCULATE(
    AVERAGEX('DAX','DAX'[RQ]),
DATESINPERIOD(Dim_Datum[Date],LASTDATE(Dim_Datum[Date]),-42, DAY)
)

This somehow gives me a calculated value of 7,69% - but its the same for all weeks. 

[rajendraongole1]

Hi @stw - can you try below measure for week

Rolling_6W_Avg_RQ =
CALCULATE(
AVERAGE('DAX'[Repair_Quote]),
DATESINPERIOD(
Dim_Datum[Date],
LASTDATE(Dim_Datum[Date]),
-6,
WEEK
)
)

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[stw]

Unfortunately, WEEK is not a valid argument. Only DAY MONTH YEAR QUARTER are available.

Also, changing the function from 

AVERAGEX('DAX','DAX'[RQ])

to

AVERAGE(DAX[RQ])

gives me an error saying 
"column RQ was not found in table dax or cannot be used here"

Maybe there is a problem with the date table and/or the connections between the tables and the calculated measure?