An Extension field on item level in a Project Invoice Request cannot be updated.
SAP Business ByDesign
Reproducing the Issue
Your PDI solution is trying to update an Extension field in CustomerProjectInvoiceRequisition-Item.node but this is not possible due to the following error: Changing data not possible; data is read-only
In order to modify the item in a Project Invoice Request the system checks the Status/LifeCycleStatusCode. If the Status/LifeCycleStatusCode of the respective Project Invoice Request is not 1 (In Preparation) an update on the Item node is not allowed.
You need to implement a check on the Status/LifeCycleStatusCode of the CustomerProjectInvoiceRequisition to ensure your PDI Solution will not execute the modification if the Status/LifeCycleStatusCode is not In Preparation.
Read Only; Changing data not possible; data is read-only , KBA , AP-CPI , Customer Project Invoice Preparation , Problem