You are not authorized to assign user &1 for system &2

What causes this issue?

You do not have sufficient authorization for the object S_USER_SAS with
activity 01 (field ACTVT) for the system &V2& (field SUBSYSTEM) and the
user group (field CLASS) for the user &V1&.

System Response

The role assignment was not changed.

How to fix this error?

Have your user administrator assign you the required authorizations and
repeat the operation.

Error message extract from SAP system. Copyright SAP SE.