Are there any items in stock?  

On the line item that you created on the sales order what is the product source defaulting to?

Hi Stephen,

Yes there is items in the stock.

While on the line item, the default product source is PO-Direct to customer

Thanks for your reply!

Try this.  I might not be ordering back to back because you have stock but that doesn't seem right.  You should be able to force back to back.    

What is the PO direct Qty set to in the Product record? I would read the field help file but WAIT... the old help is back?  "This field contains the quantity (expressed in sales units) from which the direct order will be straightforward."   

Again i would expect you could force it but...   

Hi Stephen,

I have tried allocating the value to PO direct qty but the back-to-back order option is still not available. Currently I have filed this issue to my partner and I will post their suggestion here if the issue is fixed

Thanks for your suggestion.

>>tried allocating the value to PO direct qty 

Was the po direct quantity higher than the in stock amount?

what about the product site record?  Is it set to allow back to back? 

Are the suppliers set at the product record or product site record and if product site are they set back to back?

There are some parameters but it looks like they only affect credit issues and holds. 

Hi Stephen,

Nope, I have 1000 qty available in my stock and I only assigned 10 qty to the PO direct order. 

Yes, there is a supplier assigned and the back to back is ticked.

I did some further investigation on the screen and window yesterday and I noticed that there is a heavy customization on the Sales Order screen, therefore I suspect that the customization caused the back-to-back order option to be grey out 

Thanks!

>>I only assigned 10 qty to the PO direct order. 

If the order is 11, it should go PO direct.   That's probalby not really the issue since it was zero before, but worth a shot.    

Assume product site is, like product record, set for B2B.