User &1 and Role &2 are in different Sites. The Role can't be assigned to the User.
&1 - The login name of the user.
&2 - The name of the role
An attempt has been made to assign a role to a user. However, this has failed because the user and role belongs to different sites. This will normally be caused by a call to the API User.AddRole.
The developer responsible for the business process must ensure that roles and users belong to the same site.