Error with Amazon Comprehend (Sentiment)

Hi everyone, i am trying to use the Amazon Comprehend (Sentiment) but it shows me this error:

Execute failed: Missing Authentication Token (Service: Comprehend, Status Code: 400, Request ID: f5592b7e-5d9e-4485-ae29-b11c3a53d9c8)

Is there any solution apart from having a access key or account? Or is that the only way