Can't create request for a specified user

Can't create request for a specified user

My first line of support can't create request for a specified user.
When request is created and saved, error dialog screen is reporting: "You cannot create a request for this user. The user belongs to a site for which you do not have access".

Can't see where can I change site restrictions for my tech.

What I did wrong?

                  New to ADSelfService Plus?