Fail to send proactive message after some time

[ritazh]

Error received in log when calling connector.Conversations.SendToConversationAsync after user ends conversation with a bot for some time.

Authorization for Microsoft App ID failed with status code Unauthorized and reason phrase 'Unauthorized'

This seems to occur in both Skype and Teams conversations.
Similar issue has been tracked here: microsoft/botframework-sdk#2575

[EricDahlvang]

You need to add a call to
MicrosoftAppCredentials.TrustServiceUrl(serviceUrl);
This is done automatically when you are replying to a message, but not when using the ConnectorClient