Add manual project connection to CO line

Hello,

I am trying to add a manual project connection to a customer order line for a non-inv sales part (status of CO is planned) but get the following error message (on IFS App10)

The customer order was created from the intercompany workflow (from a PO sent through MHS) - the supply code on line is “non inventory” and when trying to change for “project” supply code, following error message appears

End goal is to be able to connect my project and activity to customer order line, to proceed with the bookings of customer invoice which are supposed to rely on preposting values

If you have an idea on the reason behind this issue, please share your views :) 

Thanks

Tanya