Web api Authentication

I created successfully a web api (image bellow) then i copy the URL in the browser and its works (check image bellow)

But when I copy the URL in an incognito browse, shoe this error: 

{"resource":"\/suite\/webapi\/CWAOECClients","error":"APNX-1-4187-000","message":"Authentication failed. Please check your credentials and try again.","title":"An Error Has Occurred"}

Help please

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