Access token is used against invalid domain

I have implemented the following code in my plain JavaScript webpage:

const http = new XMLHttpRequest()

http.open("GET", "<CognitoPoolDomainName>.auth.eu-central-1.amazoncognito.com/oauth2/userInfo");
http.setRequestHeader("Authorization", "Bearer " + jwtToken);
http.send();

http.onload = () => console.log(http.responseText);
});

the jwt token can be decrypt well in https://jwt.io/.

But I am getting this error message:

{"error":"invalid_token","error_description":"Access token is used against invalid domain"}

Can you help me tin understand what token - in which format - is required by this API Endpoint? https://docs.aws.amazon.com/cognito/latest/developerguide/userinfo-endpoint.html

Many thanks!