Report Services Wont Execute My SP

Everytime I try to execute my SP in Report Services this is the message I get
I can execute it in SQL Server and have no problems at all it gives me exactly what I ask for. Help please

TITLE: Microsoft Report Designer
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An error occurred while executing the query.
Failed to convert parameter value from a String to a DateTime.

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ADDITIONAL INFORMATION:

Failed to convert parameter value from a String to a DateTime. (System.Data)

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String was not recognized as a valid DateTime. (mscorlib)



ALTER PROCEDURE [dbo].[SearchByDateLstNmDuration]
@StartDateserved datetime = null,
@EndDateserved datetime = null,
@Enter_LastName nvarchar(25) = null,
@Enter_Duration nvarchar(10) = null
AS
SELECT IR#, [Date served], [Reason for Exclusion], Duration, [First Name], [Last Name]
FROM [dbo].[Extended Exclusions]
WHERE (@StartDateserved is null or [Date served] >= @StartDateserved)
AND (@EndDateserved is null or [Date served] <= @EndDateserved)
AND (@Enter_LastName is null or [Last Name] = @Enter_LastName)
AND (@Enter_Duration is null or Duration = @Enter_Duration)