Epicor BPM LINQ in C# left outer join two tables with DefaultIfEmpty() is not working

Sorry for the thread-necro

I’m having a similar problem, I need a BPM that’ll loop through a list of a Customer’s open SO#s that do not have any POs or Jobs linked. In a BAQ, I’ve done it with couple Left Outer joins and a Where checking for null returns. But having problems converting it into a LINQ for the BPM.
I’ve tried modifying the query Nate created in another thread LINQ nullable Bool? - #6 by Randy but so far no luck.

select 
	oh.OrderNum as OrderNum,
	oh.OpenOrder as OpenOrder,
	oh.CreditOverride as CreditOverride

from OrderHed as oh
left outer join Erp.JobProd as jp 
	on oh.Company = jp.Company and oh.OrderNum = jp.OrderNum
left outer join Erp.PORel as PORel 
	on oh.Company = PORel.Company and oh.OrderNum = PORel.BTOOrderNum

where  ( jp.JobNum is null and PORel.PONum is null ) and oh.OpenOrder = 1 and oh.CustNum = 'CustVar'