Diagnosis
Relevancy to billing &V1& is not allowed for a BOS type for which aunit price contract form has been defined.

Procedure
Change the relevancy to billing. You can choose between the followingvalues for a unit price contract
' ',,Not relevant to billing
'S',,Order-related billing with down payment (without billing plan)
If you do not want to change the relevancy to billing, choose anotherBOS type with flat-rate price contract.