What causes this issue?

You have attempted to switch to the tabstrip control for partner
maintenance. The system requires a partner determination procedure for
partner maintenance, but the shipment type of the current shipment does
not contain any.
IF &[SWITCH]S4H_DOCU_ON_PREMISE& = 'X'.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

In Customizing (<DS:TRAN.VOPA>Define and assign partner determination
procedure</>), assign a partner determination procedure to the shipment
type.

Procedure for System Administrators

ENDIF.

Error message extract from SAP system. Copyright SAP SE.