Status of user &1 for system &2 is undefined (check SCUG)

What causes this issue?

A portal role for target system &V2& was assigned to user &V1&.
The CUA central system currently has no status information about this
user.
The following reasons are possible:
System &V2& was recently added to the CUA landscape and the user
comparison process was not yet completed.
User &V1& was created in the central system, but never had assignments
in System &V2&.

System Response

How to fix this error?

Start Transaction SCUG.
Make sure that target system &V2& does not have status "New".
If it has this status, use Transaction SCUG to make sure that user &V1&
was already transferred to the central system (status: "Already central
user"). If this is not the case, copy the user before continuing to
process portal roles.
If this is not the case, you can continue the transaction without
taking any other steps.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.