Your LEFT JOIN condition has a problem as both columns belong to CustomerArea. Additional to that, your CustomerArea key seems to consist on 2 columns and you're using just one.

Try this:

SELECT LocationName,

CustomerAReaName,

(CustomerFirstNAme + CustomerLastName) AS Name

FROM CustomerInfo CI

INNER JOIN CustomerLocationName CLN ON CI.LocationID = CLN.LocationID

LEFT OUTER JOIN CustomerArea CA ON CI.LocationID = CA.CustoemerLocationID

AND CI.AreaID = CA.CustomerAreaID