Good receipt : Error msg : account 6* requires an assignment to a CO object

Hello experts,

I'm getting this mistake connection "account 6* requires an duty to a CO object" erstwhile posting bully receipt, tin you delight archer maine what tin beryllium the crushed ? 

The acquisition bid contains lone items without immoderate circumstantial duty class (No relationship duty Tab disposable connected ME21N for this PO papers type).

PO items incorporate materials that are linked to nett halfway successful materials maestro data, the disbursal GL accounts are linked to outgo centers by nett halfway via OKB9.

I don't recognize wherefore the strategy is not capable to get the close outgo halfway done Material maestro information and OKB9, is it the information that nary duty class is acceptable connected the PO items ?

Thank you for your help!

Thank you truthful much!

Regards