Cannot Start Call from client app to teams user using ACS

Question

Using the guide here https://docs.microsoft.com/en-us/azure/communication-services/quickstarts/voice-video-calling/get-started-teams-interop?pivots=platform-windows

I am able to join a team meeting from my client app.

Now trying to start a 1:1 call with a teams identity on the client, to another teams identity (on teams); I've tried to use the StartCallAsync method (instead of JoinAsync) from https://docs.microsoft.com/en-us/azure/communication-services/quickstarts/voice-video-calling/get-started-with-voice-video-calling-custom-teams-client

This example is in node - I'm using C# and it looks like the most recent beta build of the SDK does NOT have the threadId property exposed.

Here is the JS code

call_ = await call_agent.startCall([{ microsoftTeamsUserId: calleeTeamsUserId.value.trim() }], { videoOptions: videoOptions, threadId: teamsThreadId });

and this link https://docs.microsoft.com/en-us/javascript/api/azure-communication-services/@azure/communication-calling/startcalloptions?view=azure-communication-services-js states that a threaded is required; however, no such threadId exists for c# SDK

The client goes from a connecting state to a disconnected state - the call never rings

Specific code to make the call

StartCallOptions startCallOptions = new StartCallOptions();
ICommunicationIdentifier[] callees = new ICommunicationIdentifier[1]
{
     new MicrosoftTeamsUserIdentifier(*****)
};
call_ = await call_agent.StartCallAsync(callees, startCallOptions);