Aws.GameLift.Realtime.Client Connect immediately returns Disconnected status

I am having a problem making a call to Aws.GameLift.Realtime.Client.Connect where it immediately returns a DISCONNECTED status and the Client.OnCloseEvent is called.

• I was expecting to receive a different status such as CONNECTING or CONNECTED_SEND_AND_RECEIVE_FAST.
• I started a game session by calling a Lambda function (as mentioned in the link below), and successfully received an endpoint, tcp port, session Id, etc and used that info to call Client.Connect, however when I check the game session logs there are no errors, and the game session just times out after 2 minutes (which is what the script is set up to do)
• My fleet is set up with TLS activated; I am specifying ConnectionType = RT_OVER_WSS_DTLS_TLS12

Is there anything else I should be looking at to determine why my attempt to "Connect" is not succeeding? (why is the Aws.GameLift.Realtime.Client.Connect being immediately disconnected, or Connection is refused?)

I'm following the instructions and basic script found here: https://docs.aws.amazon.com/gamelift/latest/developerguide/realtime-client.html

And also referring to the setup of my fleet/lambda in the instructions here: https://aws.amazon.com/blogs/gametech/creating-servers-for-multiplayer-mobile-games-with-amazon-gamelift/