3287461 - Stock transfer purchase requisition could not be converted to purchase order due to error

Below error occurs when converting stock transfer purchase requisition to purchase order in app Manage Material Coverage. 
"Stock transport requisition could not be converted.
Doc. type/item cat. NB/U (requisition) <-> NB/ (purch. order)"

SAP S/4HANA Cloud

MRP always creates PR (purchase requisition) of item category (7/U) in case of stock transfers regardless whether it is intra-company or inter-company stock transfer.
Furthermore the system always uses the document type 'NB' as default document types for all kind of PRs (external procurement/subcontracting/stock transfer) created during the MRP planning runs. This is the standard behavior of the MRP. 

If it is not allowed to convert these PRs into the desired PO document types, then either the configuration of the purchasing process has to be adjusted or the MRP has to create PRs with different document types.

Go to configuration "Define Document Types for Purchase Orders" to add entries to allow the conversion of PRs with NB/U to POs with NB/blank in purchasing to support this scenario. 
Alternatively, the document type of the PRs created by the MRP can be controlled by maintaining appropriate MRP group settings and assigning these MRP groups to concerned material. There it is possible to specify default document types for stock transfer PRs like 'UB' for instance. 

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