Error Code 403

Hello and a Happy new year,

I am trying to connect to Cesium ion for Unreal but I get the following error. Can you please advise if I am missing something, I have tried disabling firewall and antivirus but still getting the same error.


Not authorized!

The authorization failed with the following error message: The server returned an error code: 403.

Please close this window and return to Cesium for Unreal.

If the problem persists, contact our support at



The most likely cause of errors like that is that your network requires the use of a proxy in order to do HTTP POST requests, and Unreal Engine isn’t using that proxy. Unreal Engine unfortunately doesn’t automatically use a proxy if one is configured on your system. I can’t test it as I don’t have a proxy myself, but some users have reported success in the past by setting the HTTP_PROXY and HTTPS_PROXY environment variables.