Give this a try. Plese note, it is untested. I don't have your tables or data. It passes a syntax check, but that's all I could do.

Changes are in red.

Select D.ConsultantID

,D.Downlinelevel

,D.ConsultantName

,D.EffectiveDate

,B1.FirstName + ' ' + B1.LastName AS SponsorName

,D.SponsorID

,D.AchievedTitle

,ISNULL(CONVERT(CHAR(10),D.CurrentLevelAchieveDate,101),'') AS AchieveDate

,ISNULL(Convert(Char(10),D.BumpupDate,101),'') as BumpupDate

,ISNULL(Sum(CASE

WHEN O.OrderCreateDate Between @QuarterStartDt And @QuarterEndDt THEN O.PartOneTotal

ELSE 0

END),0) AS QuarterToDate_total

,ISNULL(Sum(CASE

WHEN O.OrderCreateDate Between @MonthStartDt And @MonthEndDt THEN O.PartOneTotal

ELSE 0

END),0) AS MonthToDate_Total

,D.ConsultantXID

,D.SponsorXID

,ISNULL(QuarterVolume,0) AS QuarterToDate_Volume

,ISNULL(MonthVolume,0) AS MonthToDate_Volume

,D.Active

,ISNULL(r.RepFlag,' ') AS RepFlag

,CASE StatusID

WHEN 'Active' THEN ''

WHEN 'Home Office' THEN ''

WHEN 'New, Non Active Consultant' THEN ''

ELSE StatusID

END AS StatusID

,CONVERT(Varchar(10),D.NACDate,101) as AgreementDate

,CASE WHEN @PeriodDate Between @CurrMonthStartDt AND @CurrMonthEndDt THEN 'X'

ELSE ' '

END AS ShowFlag

INTO #DLLevel

-- not much point in nolock on a temp table. Hint only applies to a single table

FROM #Downline D with (nolock)

LEFT OUTER JOIN uvw_DownlineOrder O ON D.ConsultantID = O.ConsultantID

LEFT OUTER JOIN Repromotes r ON d.ConsultantID = r.ConsultantID AND r.repflag = 'X'

-- Was there a reason for the uvwConsultantDownLine table?

-- Took it out of the subquery, because it didn't appear to be necessary.

-- Hence subquery reduced to one table and joined in.

LEFT OUTER JOIN dbo.consultant AS B1 ON D.SponsorID = B1.ConsultantID

-- Added from select clause. Merged 2 subqueries into 1, since 1 was a subset of the other

LEFT OUTER JOIN (SELECT ConsultantID,

SUM(v.PartOneTotal) AS QuarterVolume,

SUM (CASE WHEN V.OrderCreateDate Between @MonthStartDt And @MonthEndDt THEN PartOneTotal ELSE 0 END) AS MonthVolume

FROM uvw_DownlineOrder V

INNER JOIN SharedDimension.dbo.DimOrderType AS T ONV.OrderTypeXID = T.XID

WHERE (T.OrderType != 'Credit')AND V.OrderCreateDate Between @QuarterStartDt And @QuarterEndDt

GROUP BY ConsultantID) VT ON D.ConsultantID = VT.ConsultantID

-- Missing brackets here. AND has precedence over OR.

WHERE ((D.Active = 1) OR (D.DeactivationDate BETWEEN @MonthStartDt AND @MonthEndDt))

AND r.AchieveLevel >= 4

-- Might need some modification

GROUP BY D.ConsultantID ,D.Downlinelevel

,D.ConsultantName

,D.SponsorName

,D.EffectiveDate

,D.SponsorID

,D.AchievedTitle

,D.CurrentLevelAchieveDate

,D.BumpupDate

,D.NACDate

,D.ConsultantXID

,D.SponsorXID

,D.Active

,r.RepFlag

,D.StatusID