Consuming RESTful web services with Unity webGL build

I am trying to consume a RESTful web service with JWT authentification in my Unity app, built as an webGL-app. It works perfectly fine when I run the app in Game-Mode. Communication is working well. Unfortunately this changes when I build it as webGL and upload to github to run as webpage and test. It will give me a 400 forbidden message when I try GET. Any idea where this is coming from? The API in question is: https://www.opensensors.com/