The user belongs to a site for which you do not have access

The user belongs to a site for which you do not have access

When trying to create a request for a specific requester I get this error. The requester has these symbols in his name [ ]

Would this be the issue and how could I resolve it? The department that doesn't exist in the sites of SD+ is written between these brackets.

I am running Service Desk 9.2 Build 9211 with an MSSQL database.

                  New to ADSelfService Plus?