MS SQL - JOIN show months that doesn't have data

I am having a new problem with SQL JOINS.

Here is my scenario.

I have a report, where I need to show sales performance for a specific customer. The report shows the sales performance per month.

Please look at my result set:

This is the sales report for customer AFP035. As you can see there are months that are not showing. I am required to include those months that doesn't have data(NULL).

Here what I have tried. I created a month table where I maintained the months.

And then I did a LEFT JOIN. Seems strange because it doesn't show the desired result. From what I understand LEFT JOIN should show the NULL values. And I am wrong.

Please see my query:

select  CustNm as company,
        Cust as customer,
        Cust as custCode,
        Mon,
        case
        when Mon = 1 THEN 'January'
        when Mon = 2 THEN 'February'
        when Mon = 3 THEN 'March'
        when Mon = 4 THEN 'April'
        when Mon = 5 THEN 'May'
        when Mon = 6 THEN 'June'
        when Mon = 7 THEN 'July'
        when Mon = 8 THEN 'August'
        when Mon = 9 THEN 'September'
        when Mon = 10 THEN 'October'
        when Mon = 11 THEN 'November'
        when Mon = 12 THEN 'December'
        end as 'month',
        Yr as 'year',
        Mon as monthCheck,

        case
        when NetSales IS NULL THEN 0
        else NetSales
        end as netSales,

        case
        when PrvYrSales IS NULL THEN 0
        else PrvYrSales
        end as prevYearSales,

        case
        when SalesGrwth IS NULL THEN 0
        else SalesGrwth * 100
        end as salesGrowth,

        case
        when YrBfrLst IS NULL THEN 0
        else YrBfrLst
        end as yearBeforeLast,

        case
        when BfrLstGrwth IS NULL THEN 0
        else BfrLstGrwth * 100
        end as yearBeforeLastGrowth

from    BigEMasterData.dbo.monthtmp as a

        left outer join BigESales.dbo.tbl_ReportCOMPANYperCust as b
        on b.Mon = a.monthNo
        or b.Mon is null

The result is the screenshot above.

Would you help me with this or at least enlighten me why I am not getting the desired result?

Thank you so much. Any suggestion would be highly appreciated.

EDIT: SOLVED: with Yogesh's help Thankyou.

;WITH CTE AS (
    SELECT * FROM tbl_ReportCOMPANYperCust r 
    WHERE Cust = 'AFP035'
	and Yr = 2016
)

SELECT 
       r.CustNm as company, r.Cust as customer, r.Cust as custCode, 
       a.monthNo, a.monthName, r.Yr as Year, 
       COALESCE(NetSales, 0) as netSales, 
       COALESCE(PrvYrSales, 0) as prevYearSales, 
       COALESCE(SalesGrwth*100, 0) as salesGrowth, 
       COALESCE(YrBfrLst, 0) as yearBeforeLast, 
       COALESCE(BfrLstGrwth*100, 0) as yearBeforeLastGrowth  
FROM BigEMasterData.dbo.monthtmp a
LEFT OUTER JOIN CTE r on r.Mon = a.monthNo

Here is the result. :