No SAP user maintained for partner '& & &'

What causes this issue?

An SAP user was not specified for notification in the EDI partner
profile (inbound) for the partner '&V1& &V2& &V3&'.

System Response

A text message was not sent.

How to fix this error?

Enter an SAP user for the text message in the EDI partner profile
(inbound).
Logical message 'TXTRAW', receiver of notifications: type 'US'.

Error message extract from SAP system. Copyright SAP SE.