scalar variable error after it has been declared

I'm running Microsoft SQL Server 17.7 and I keep getting an error message when trying to filter my data set by a date range with a where clause using a scalar variable. I declared both variables but I continue to get this error message "Must declare the scalar variable "@startDate". I'm guessing I'm not declaring the scalar variable correctly. Please assist.

DECLARE @MatterList NVARCHAR(100) = '(21940-00035)'
declare @startDate datetime = '1/1/2012'
declare @endDate datetime = '6/30/2015'

SELECT @MatterList = NULL 
WHERE @MatterList = ''

DROP TABLE IF EXISTS #listMatter
DROP TABLE IF EXISTS #Matterlist

CREATE TABLE #MatterList (rowid int identity, MatterNumber nvarchar(20))
CREATE INDEX tMatterListIndex_MatterNumber on #MatterList (MatterNumber)

select value into #listMatter from 
string_split(replace(replace(replace(@MatterList,'(',''),')',''), ' ' , ''), ',')


Insert into #MatterList (MatterNumber)
select m.Number as MatterNumber
from #listMatter lm
inner join Matter m with (nolock) on lm.value = m.Number
where m.Number not in (select matterNumber from #MatterList)

If OBJECT_ID('tempdb..#fees_detail') is not NULL drop table #fees_detail
GO

SELECT DISTINCT 'Fees' AS [type],
            t.code AS tudef2,
            tc.PostDate AS bfindt,
            tc.IsActive AS isActive,
            tc.IsNoCharge AS isNoCharge,
            m.OpenDate AS mopendt,
            m.CloseDate AS mclosedt,
            m.ContactInfo AS 'matter_contact',
            a.DESCRIPTION AS 'matter_arrangement',
            m.BillingInstruc AS 'billing_instructions',
            m.Comments AS 'terms',
            m.Number AS 'matter_id',
            c.DisplayName AS 'client_name',
            m.DisplayName AS 'matt_desc',
            m.Narrative_UnformattedText AS 'matt_nar',
            btk.Number AS 'batty_id',
            btk.DisplayName AS 'batty_name',
            tk.Number AS 'tk_id',
            tk.DisplayName AS 'tk_name',
            td.HireDate AS 'tkemdate',
            title.DESCRIPTION AS 'tktitle',
            htitle.DESCRIPTION AS 'htitle',
            CASE htitle.DESCRIPTION 
                WHEN 'partner' 
                    THEN 1 
                WHEN 'associate' 
                    THEN 2
                WHEN 'summer assoc.' 
                    THEN 3 
                WHEN 'staff counsel' 
                    THEN 4 
                WHEN 'paralegal' 
                    THEN 5
                WHEN 'als' 
                    THEN 6 
                WHEN 'CSS admin' 
                    THEN 7 
                WHEN 'legal graphics' 
                    THEN 8
                WHEN 'library' 
                    THEN 9 
                WHEN 'case clerks' 
                    THEN 10
                WHEN 'lit analyst' 
                    THEN 11 
                        ELSE 12 
            END AS 'tktitle_sort',
            d.DESCRIPTION AS 'mdept',
            pg.DESCRIPTION AS 'mprac',
            o.DESCRIPTION AS 'mloc',
            tc.TimeIndex AS 't_index',
            tc.WorkDate AS 'worked_date',
            CONVERT(VARCHAR(6),tc.workdate,112) AS 'worked_period',
            tc.WorkHrs AS 'tworkhrs',
            tc.WorkRate AS 'tworkrt',
            tc.WorkAmt AS 'tworkdol',
            tc.WIPRemoveDate AS 'tbilldt',
            tc.WIPHrs AS 'tbillhrs',
            tc.WIPRate AS 'tbillrt',
            tc.WIPAmt AS 'tbilldol',
            tc.Narrative_UnformattedText AS 'time_desc',
            '' AS 'ccode',
            '' AS 'codesc1',
            CASE 
                WHEN tc.IsNB = 1 
                    THEN 0.00 
                        ELSE  tc.WIPAmt - tc.WorkAmt 
            END AS 'adj'
INTO  #fees_detail
FROM timecard tc WITH (NOLOCK)
            INNER JOIN matter AS m WITH (NOLOCK) 
            ON tc.matter = m.mattindex
            INNER JOIN #MatterList AS tm 
            ON m.Number = tm.MatterNumber
            INNER JOIN mattdate AS md WITH (NOLOCK) 
            ON m.MattIndex = md.MatterLkUp 
                AND CONVERT(DATE,GETDATE()) BETWEEN  md.NxStartDate AND md.NxEndDate
            INNER JOIN client AS c WITH (NOLOCK) 
            ON m.client = c.ClientIndex
            INNER JOIN PracticeGroup AS pg WITH (NOLOCK) 
            ON md.PracticeGroup = pg.Code
            INNER JOIN Department AS d WITH (NOLOCK) 
            ON md.Department = d.Code
            INNER JOIN Arrangement AS a WITH (NOLOCK) 
            ON md.Arrangement = a.Code
            INNER JOIN Office AS o WITH (NOLOCK) 
            ON md.Office = o.Code
            INNER JOIN Timekeeper AS tk WITH (NOLOCK) 
            ON tc.Timekeeper = tk.TkprIndex
            INNER JOIN TkprDate AS td WITH (NOLOCK) 
            ON tk.TkprIndex = td.TimekeeperLkUp 
                AND CONVERT(DATE,GETDATE()) BETWEEN td.NxStartDate AND td.NxEndDate
            INNER JOIN TkprDate AS htd WITH (NOLOCK) 
            ON tk.TkprIndex = htd.TimekeeperLkUp 
                AND tc.WorkDate BETWEEN htd.NxStartDate AND htd.NxEndDate
            INNER JOIN Timekeeper AS btk WITH (NOLOCK) 
            ON md.BillTkpr = btk.TkprIndex
            INNER JOIN title WITH (NOLOCK) 
            ON td.title = title.code
            INNER JOIN title AS htitle WITH (NOLOCK) 
            ON htd.title = htitle.code
            LEFT OUTER JOIN task AS t WITH (NOLOCK) 
            ON tc.Task = t.TaskID

Where tc.WorkDate between @startDate and @enddate
ORDER BY m.Number, tc.WorkDate, tc.TimeIndex

SELECT  
[type], tudef2, bfindt, isActive, isNoCharge, mopendt, mclosedt, matter_contact, 
matter_arrangement, billing_instructions, terms, matter_id, client_name, matt_desc, matt_nar, 
batty_id, batty_name, tk_id, tk_name, tkemdate, tktitle, htitle, tktitle_sort, mdept, mprac, 
mloc, t_index, worked_date, worked_period, tworkhrs, tworkrt, tworkdol, tbilldt, tbillhrs, 
tbillrt, tbilldol, time_desc, ccode, codesc1, adj
FROM #fees_detail   

ORDER BY 29