Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. (Microsoft SQL Server)

Question

I am getting the error message, "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. (Microsoft SQL Server)". I am attaching the stored procedure. Can anyone see where the syntax may
be causing this.
USE [ReportData]
GO
/****** Object: StoredProcedure [PDI].[usp_MJTestTop10_Select] Script Date: 04/23/2015 10:35:43 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
--USE [ReportData]
--GO
--/****** Object: StoredProcedure [PDI].[usp_MJTestTop10_Select] Script Date: 04/23/2015 08:22:26 ******/
--SET ANSI_NULLS ON
--GO
--SET QUOTED_IDENTIFIER ON
--GO
ALTER PROCEDURE [PDI].[usp_MJTestTop10_Select]
@StartDate DATE,
@EndDate DATE,
@Location VARCHAR
AS
DECLARE @CalendarKey TABLE (
Calendar_Key int,
Organization_Key int,
Day_Date DATETIME
BEGIN
INSERT INTO @CalendarKey
SELECT C.calendar_key,
O.Organization_Key,
C.Day_Date AS DATETIME
FROM pdi.PDI_Warehouse_952_01.dbo.calendar C,
pdi.PDI_Warehouse_952_01.dbo.Organization O
where @EndDate is not null
and C.Day_Date BETWEEN @StartDate and @EndDate
or @EndDate is null
and C.Day_Date = @StartDate
END
SELECT CAST(C.Day_Date as DATE) as [Memo Date],
--C.calendar_key,
ISNULL(CAST(MBH.Transaction_Number as VARCHAR), 'Unknown') as [Memo Number],
O.Site_id,
O.Site_desc,
--p.Product_Key,
p.UPC as [UPC],
(CAST(P.Department_ID as VARCHAR) + ' ' + CAST(P.Category_ID as VARCHAR) + ' ' + CAST(P.Sub_Category_Id as VARCHAR)) as [D C S],
ISNULL(CAST(IPF.Vendor_Key as VARCHAR), 'Unknown') as [Vendor Code],
--ISNULL(CAST(V.Vendor_Desc as VARCHAR), 'Unknown') as [Vendor Desc],
ISNULL(P.Item_Desc, 'Unknown') as [Description],
ISNULL(P.Size_Desc, 'Unknown') as [Size],
ISNULL(RTrim(Cash.Cashier_Name), 'Unknown') as [Associate],
ISNULL(CONVERT(INT, IIF.Beg_Inv_Qty, 0), '0') as [Old Qty],
ISNULL(CONVERT(INT, IIF.End_Inv_Qty,0), '0') as [Adj Qty],
ISNULL(CONVERT(INT, IIF.End_Inv_Qty - IIF.Beg_Inv_Qty, 0), '0') as [Dif Qty]
FROM pdi.PDI_Warehouse_952_01.dbo.Item_Sales_Fact ISF
INNER JOIN pdi.PDI_Warehouse_952_01.dbo.Product P ON ISF.Product_Key = P.Product_Key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Organization O ON ISF.Organization_key = O.organization_key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Item_Purchases_Fact IPF ON ISF.Product_key = IPF.Product_Key
AND ISF.Organization_key = IPF.Organization_key
AND ISF.Calendar_key = IPF.Calendar_key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Item_Inventory_Fact IIF ON ISF.Product_Key = IIF.Product_Key
AND IIF.Product_Key = P.Product_Key
AND ISF.Organization_key = IIF.Organization_Key
AND ISF.Calendar_key = IIF.Calendar_Key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Calendar C ON ISF.calendar_key = C.calendar_key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Cashier Cash ON ISF.Organization_Key = Cash.Organization_Key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Cashier_Metric_Hourly_Dept_Snapshot CMH on Cash.Organization_Key = CMH.Organization_Key
AND Cash.Cashier_Key = CMH.Cashier_Key
AND ISF.Calendar_Key = CMH.Calendar_Key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.MarketBasket_Header MBH ON ISF.Calendar_Key = MBH.Calendar_Key
AND ISF.Organization_Key = MBH.Organization_Key
AND Cash.Cashier_Key = MBH.Cashier_Key
LEFT JOIN pdi.PDI_Warehouse_952_01.dbo.Vendor V ON IPF.Vendor_Key = V.Vendor_key
AND IPF.Calendar_Key = C.Calendar_Key
LEFT JOIN @CalendarKey CK ON ISF.Calendar_Key = ck.Calendar_Key
AND ISF.Organization_Key = CK.Organization_Key
WHERE C.calendar_key = CK.Calendar_Key
ORDER BY
O.Location_ID,
C.Day_Date,
IPF.Vendor_Key,
P.UPC,
P.Size_Desc

Answer 1

Some additional comments. 
@Location VARCHAR
Look closely at this.  How many characters can @Location contain?  You did not specify, so perhaps you think some appropriately large default value is used.  Guess again. You did a similar thing with cast (multiple times) - which is handled
differently.  Don't be lazy.
WHERE C.calendar_key = CK.Calendar_Key
Go review the join to the CK table.  It is an outer join.  Yet you have included criteria in the where clause that requires a match in the unpreserved (@CalendarKey aka CK) table.  This effectively transforms that join from outer to inner.
Was that intentional? Probably, but then you don't need to use an outer join
FROM pdi.PDI_Warehouse_952_01.dbo.calendar C,
pdi.PDI_Warehouse_952_01.dbo.Organization O
Evolve.  We do not join in the where clause any longer.  You should be joining using join operators.  And perhaps more importantly, why do you need to dump a resultset into a table variable at all?  Note that your join is a cross join
since there is no relationship between calendar and Organization - intentional? Given the rest of the logic, it seems that you don't really need to do this.
ISNULL(CONVERT(INT, IIF.End_Inv_Qty,0), '0') as [Adj Qty],
Go review the documentation for convert.  You supply a style, but does it do anything?  We don't know what datatype End_Inv_Qty is, but I assume it is numeric (and not float).  So what do you intend?  And you convert it to integer but
use a character '0' in the isnull function.  Your lack of consistency can lead to issues that are difficult to find and resolve.
CAST(C.Day_Date as DATE)
Why are you doing this? You defined the column in your table variable as datetime.  You cast the value you use to populate this column to datetime.  I'm guessing that you only really care about the date portion.  The name you used for the
column implies this.  So why bother with datetime in the first place?
And one last suggestion. If you disallow the use of NULL for the @EndDate argument (simply supply the same value for both date arguments) you can simplify the logic that populates your table variable (or its replacement) and greatly eliminate the confusion
and chance for errors that nullability requires.