Hello Kristian,
Could you please try pinging to the
developers.google.com to see if your system is able to reach our servers using terminal/console. If that is not working then it might be the problem with your network. You have to switch to a different network. If you are able to reach, then it mush be a problem with the browser/check if cross origin is turned on/try incognito window/use different browser to troubleshoot this.
Also, please try accessing the URL from a different browser/system using different network as none of the advertisers reported any issues while accessing the documentation looks like there is no problem at our end.
Please give it a try and let me know if you are still facing any issues.