Lambda Authorizer Always Returning Unauthorized

I have a python lambda authorizer with the following code:

def lambda_handler(event, context):
    return {
        "isAuthorized": True,
        "context": {
            "exampleKey": "exampleValue",
        }
    }

It is connected to an API Gateway route with the following configuration:

It always return {"message":"Unauthorized"} when the /dataset/classes route is used. Why doesn't it continue to the integrated function if isAuthorized is always set to true?