Purchase Org Missing error

Hi All,

we have the Purchase group & Purchase Org maintained in the Purchase org structure (ppoma_bbp) but when creating shopping cart i'm getting the following errors

1- purchasing org for follow-on doc missing

2- purchasing group O xxxxx(org unit ID of Pur group) not assigned to Purchase Org.

3- no purchasing org exists.

does anyone have any idea on this. appreciate any help on this.

Thanks