WebViewControl: The RPC server is unavailable

We are trying to implement Edge embedding (C++) based on the example here: https://blogs.windows.com/msedgedev/2018/05/09/modern-webview-winforms-wpf-apps/#DuQiIVZ5t0Gjl9Ju.97

But we have an issue where the example code above fails to initialize the WebViewControl. both the async and sync initialization fails for the same reason: Exception thrown at 0x00007FFA48985299 (KernelBase.dll) in Win32WebViewSampleApp.exe: 0x800706BA: The RPC server is unavailable.

We have verified the RPC services are running, and the firewall is disabled. There also doesn't appear to be a general issue with COM/OLE on the machine as our old implementation using WebBrowser IEControl works without issues.

We are using Windows 10 Enterprise build 17758

Any help would be greatly appreciated. Thanks in advance.