Webclient offline download fails

I'm following the instructions here to download the webclient to install on a server without internet https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/remote-desktop-web-client-admin#how-to-install-the-remote-desktop-web-client-without-an-internet-connection and getting an error when running Save-RdWebClientPackage "MethodInvocationException: Exception calling "DownloadFile" with "2" argument(s): "An exception occurred during a WebClient request.""