DataSource Controls :: Conversion Failed From Converting Datetime To Character String

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go
ALTER PROCEDURE [dbo].[SP_ORDER_LIST]
@EmailId nvarchar(50)
AS
begin
declare @Id int
set @Id = (select SellerId from cart_seller_master where EmailId = @EmailId )
select
CTD.OrderId,CTD.Product_code,
CPM.product_name,CTD.Quantity,CTD.Orderdate,
case when convert(datetime,isnull(CTD.DispatchedDate,null)) is null then 'Not Dispatched'
end DispatchedDate ,
case when convert(datetime,isnull(CTD.DeliveryDate,null)) is null then 'Not Dispatched'
end DeliveryDate
from cart_Product_master as CPM
left outer join cart_Transaction_details as CTD on ctd.product_code=cpm.product_code
where CPM.SellerId = 1
group by CTD.OrderId,CTD.Product_code,
CPM.product_name,CTD.Quantity,CTD.Orderdate,
CTD.DispatchedDate,CTD.DeliveryDate
end