mysql sum case not working - mysql

Question

I am working on a mysql query using sum case. The query works for some of the cases but not for one case.
select orders.orderid, campers.description, dealers.name, orders.act_delivery,
sum(case orderitems.std
when 0 then
(case when orderitems.price = 0 then retail_price.price * orderitems. qty else orderitems.price * orderitems.qty end)
when 1 then
(case when orderitems.origqty = 0 then
0 else
(case when orderitems.price = 0
then retail_price.price * (orderitems.qty - orderitems.origqty)
else orderitems.price * (orderitems.qty - orderitems.origqty)
end)
end)
when 2 then
0
else
(case when orderitems.deletedprice = 0 then retail_price.price * orderitems. qty else orderitems.deletedprice * orderitems.qty end)
end) as retail
from orderitems, orders, dealers, campers, products, retail_price
where orderitems.orderid = orders.orderid
and orderitems.productid = products.prodid
and orderitems.productid =retail_price.prodid
and orders.dealerid = retail_price.dealer
and orders.dealerid = dealers.dealerid
and orders.camper = campers.camperid
and act_delivery > 0
and orderitems.std in (0, 1, 2)
and orders.dealerid not in (1, 9, 10, 12,15,16)
and spares_od = 0
and orders.act_delivery > '2016-10-01'
and orders.act_delivery <= '2016-10-31'
group by orders.orderid,orders.dealerid, orders.act_delivery order by orders.act_delivery, orders.orderid
The problem occurs when orderitems.std = 3. In either case I cannot get a result.
All other cases appear to be working correctly.