Dotnet sample - bad gateway / 404s on smba.trafficmanager.net

[graemefoster]

Description

Hi,
I'm getting errors running the dotnet sample when I use a devtunnel to expose my /messages endpoint to A365 and create an instance of my agent using Teams.

I can see lifecycle notification events pushing through the system, however:

• My agent is not called when I try converse with it in teams.
• If I try to send an activity on a lifecycle event I receive a 502 Bad Gateway from smba.trafficmanager.net
• I do receive a notification from Word telling me my user is trying to contact my agent
• If I respond to this I receive a 404 from smba.trafficmanager.net

Everything works in the playground. No issues at-all.

Any tips on where to go next?

Thanks,

Graeme

Expected behavior

No response

SDK Version

Latest

Language/Runtime

.NET 8 and 10

OS

MAC OS 21

How to Reproduce

1. Use Microsoft Agent Framework dotnet sample
2. Use a365 to config, setup and deploy the agent
3. Run agent with a devtunnel messaging endpoint

Output

POST https://smba.trafficmanager.net/amer/7cd964e4-a3be-4627-a8df-2b8371609081/v3/conversations/<large-id> HTTP/1.1

HTTP/1.1 502 Bad Gateway
Content-Length: 0
Server: Microsoft-HTTPAPI/2.0 Microsoft-HTTPAPI/2.0
Date: Sat, 21 Feb 2026 07:07:58 GMT

Microsoft.Agents.Core.Errors.ErrorResponseException: ReplyToActivity operation returned an invalid status code '(502) BadGateway'
         at Microsoft.Agents.Connector.RestClients.ConversationsRestClient.ReplyToActivityAsync(String conversationId, String activityId, IActivity body, CancellationToken cancellationToken)
         at Microsoft.Agents.Connector.RestClients.ConversationsRestClient.ReplyToActivityAsync(IActivity activity, CancellationToken cancellationToken)
         at Microsoft.Agents.Builder.ChannelServiceAdapterBase.SendActivitiesAsync(ITurnContext turnContext, IActivity[] activities, CancellationToken cancellationToken)
         at Microsoft.Agents.Builder.TurnContext.<>c__DisplayClass34_0.<<SendActivitiesAsync>g__SendActivitiesThroughAdapter|1>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.Agents.Builder.TranscriptLoggerMiddleware.<>c__DisplayClass2_0.<<OnTurnAsync>b__0>d.MoveNext()
      --- End of stack trace from previous location ---
         at Microsoft.Agents.Builder.TurnContext.SendActivityAsync(IActivity activity, CancellationToken cancellationToken)
         at Microsoft.Agents.Builder.TurnContext.SendActivityAsync(String textReplyToSend, String speak, String inputHint, CancellationToken cancellationToken)
         at Agent365AgentFrameworkSampleAgent.Agent.MyAgent.OnLifecycleEvent(ITurnContext turnContext, ITurnState turnState, AgentNotificationActivity agentNotificationActivity, CancellationToken cancellationToken) in /Users/g/code/github/microsoft/Agent365-Samples/dotnet/agent-framework/sample-agent/Agent/MyAgent.cs:line 117

Screenshots

No response

Code of Conduct

• I agree to follow the Microsoft Open Source Code of Conduct.