In order to use Barcode Search to locate transactions at certain locations, the Admin User will first have to be assigned a role that has access to "Basic Support". Green indicates that this permission is currently enabled.
Aside from that, the specific Admin User will also need the Locations or Location Groups that they require access to in their account, under Settings > Admin Users > Specific User. Only locations/groups listed here yield results in Barcode Lookup.
Note: If you have a franchisee that needs access to multiple locations, it is advised to create a Location Group, and use that when configuring the user.