Error "Field REJECTION_REASON_CODE cannot be changed" occurs when mass-rejecting sales orders via the "Mass Change of Sales Documents" app.
SAP S/4HANA Cloud
It is the current standard design of the "Mass Change of Sales Documents" app that if any one of the sales order items has a non-editable "Reason for Rejection" field, the rejection of the sales order will fail.
As explained in the "Cause" part, it is the current design of the "Mass Change of Sales Documents" app.
REJECTION_REASON_CODE, Reject, Sales order, Mass change of sales documents, Non-editable, Reason for rejection , KBA , SD-SLS-MCC-2CL , Mass Changes of Sales Documents (Public Cloud) , Problem
SAP S/4HANA Cloud all versions