API and Demo account

[Doge]

I've created a demo account to test integrating the API with my web app and I don't get a valid response from the Authentication endpoint.

 

The url I'm using is: https://demo-api.ig.com/gateway/deal/session and the correct api key is being sent but I get this response

{

    "statusCode": 401,

    "response": null

}

When I make the same request using my live account api key to the live api url, I get the correct response.

 

Can anyone suggest what I need to do to get the demo account working on the demo API?