Brain freeze... I added two more columns to the below listed query and getting the following error:

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, or when the subquery is used as an expression.

What am I missing?

Thank you,
DAniel

select ....,
DSPQOH = (select (NJUseable + NVUseable) from ItemMst  
             join PItems on ItemMst.DSP = PItems.ItemNo join History on PItems.EDPNo = History.EDPNo  
             where itemmst.EDPNo = ItemMst.EDPNo),  
NFSQOH = (select (NJUseable + NVUseable) from ItemMst  
             join PItems on ItemMst.NFS = PItems.ItemNo join History on PItems.EDPNo = History.EDPNo  
             where itm.EDPNo = ItemMst.EDPNo) 

From itemmst itm 
	left join DS1.dbo.WebCrawler wc on itm.ItemNo = wc.AMSSKU
	join history on itm.EDPNo = History.EDPNo
	join ProdType on itm.prodtype = prodtype.codno
	join ProdFam on itm.prodfam = prodfam.codno
	join PItems on itm.EDPNo = PItems.EDPNO
	join poffers on PItems.edpno = poffers.edpno
	join forecast on PItems.edpno = forecast.edpno
	join VendorMst on PItems.PV = VendorMst.VendNo
	join plastpo on pitems.edpno = plastpo.edpno
Where PItems.edpno = 44181