Getting error 0x204 when user try to connect to Azure virtual Desktop

Question

Getting error 0x204 when user try to connect to Azure virtual Desktop

Mario Velazquez 20

We have been using Azure Virtual Desktop for several months, however today all our users started getting error 0x204 when trying to connect to Azure Virtual Desktop. Our Virtual Hosts are in Canada East.

Mario Velazquez 20 Reputation points

2026-04-28T19:46:54.4566667+00:00

Also we are seeing this errors in the "connection Diagnostics" insights for the Host pool

<personal info>
Himanshu Shekhar 6,145 Reputation points Microsoft External Staff Moderator

2026-04-28T20:10:02.65+00:00
Mario Velazquez - From your screenshots: The Remote Desktop client is failing with Error code: 0x204 and shows an Activity ID and timestamp in the error details.

In Azure Virtual Desktop > Host pool > Insights / Connection Diagnostics, the top errors in the last 12 hours include entries sourced from RDGateway (for example ConnectionFailedServerDisconnect), RDStack (for example StackCrash), and Client (for example TransportClosedUnexpectedly (516)), with a message indicating the network connection between the Session Host and the service was unexpectedly terminated.

These signals point to a connection path problem (client > AVD gateway/service > session host) rather than a user‑specific configuration issue, since the impact is “all users.”

Check Azure Service Health / Azure status first

Microsoft’s AVD troubleshooting guidance explicitly recommends checking Azure status and Azure Service Health before deeper troubleshooting to confirm whether there is an active platform incident affecting the service. [learn.microsoft.com]

In the Azure portal, review Service Health for items affecting Azure Virtual Desktop and related dependencies for the time window when the failures began.

Confirm session hosts can reach required AVD endpoints (outbound)

Microsoft documents that Azure Virtual Desktop requires allowing specific FQDNs and endpoints for both session hosts and end-user devices, and notes that these can be blocked by firewalls or proxy services.
Microsoft also states: Azure Virtual Desktop deployments where the required FQDNs/endpoints are blocked are not supported. [learn.microsoft.com]

Validate outbound connectivity from the session host VMs to the required AVD endpoints listed in Microsoft documentation. [learn.microsoft.com]

If you use an enterprise firewall/proxy/NVA, ensure it is not blocking the required FQDNs/endpoints.

Understand the connection model (why outbound connectivity matters)

Microsoft documents that AVD uses a reverse connect transport model. Unlike traditional on‑prem RDS deployments, reverse connect does not use an inbound TCP listener for RDP it relies on outbound connectivity from the session host to the Azure Virtual Desktop infrastructure over HTTPS. [learn.microsoft.com].

If outbound HTTPS access from the session hosts (or required name resolution/proxy traversal) is interrupted, you can see gateway/service disconnects and client transport closures similar to what your Connection Diagnostics view is reporting.

Ensure AVD diagnostics are enabled and review “Connections” / “Errors” - Microsoft supports sending Azure Virtual Desktop diagnostics to Log Analytics, including categories such as Connections and Errors, to analyze connection attempts and failures. [learn.microsoft.com]

Confirm the host pool has diagnostics flowing to Log Analytics and review Connections and Errors around the time the issue started. [learn.microsoft.com]. Microsoft also documents that connections that don’t reach Azure Virtual Desktop won’t show up in diagnostics (because diagnostics is part of the AVD service path). [learn.microsoft.com]. If you see little/no data at the time of failure, that itself can indicate the connection is failing before reaching AVD.

Remote Desktop client window shows a banner indicating the Remote Desktop client is approaching end of support and recommends using Windows App. Microsoft has published guidance that the Remote Desktop client for Windows (standalone MSI) reaches end of support on March 27, 2026 for commercial clouds and advises migrating users to Windows App for continued access to Azure Virtual Desktop resources. [techcommun...rosoft.com]

This banner is a lifecycle notice. It does not, by itself, prove the cause of today’s outage. However, moving to the supported client is aligned with Microsoft guidance. [techcommun...rosoft.com]

Please capture and provide the following below (via private messages)

One failing user’s Activity ID from the Remote Desktop error details (your screenshot shows an Activity ID field).

The approximate UTC time window when the issue started (your screenshot includes a timestamp line).

A snapshot/export of the Connection Diagnostics errors shown (RDGateway / Client / RDStack entries) during the failure window.

Confirmation whether any network/security change occurred today that could affect outbound access (proxy/firewall policy update, routing/UDR change, TLS inspection policy change, DNS/proxy configuration change).

Recommended links please check -

Check Service Health for AVD-related advisories/incidents. [learn.microsoft.com]

Validate outbound endpoint access for session hosts and end-user devices against Microsoft’s required FQDNs/endpoints list (and ensure these are not blocked). [learn.microsoft.com]

Confirm you’re aligned to AVD’s reverse connect connectivity expectations (outbound HTTPS is required). [learn.microsoft.com]

Review Log Analytics diagnostics (Connections/Errors) for correlation with the failure window. [learn.microsoft.com]

Begin migrating users to Windows App in line with Microsoft’s published support timeline for the Remote Desktop client

2 answers

Your answer

Mario Velazquez 20 Reputation points

2026-04-28T19:46:54.4566667+00:00

Also we are seeing this errors in the "connection Diagnostics" insights for the Host pool

<personal info>

Answer 1

Hello everyone,

First of all thank you for your help and assistance.

It turned out that it was an issue introduced by a Hotfix deployment by the Azure Virtual Desktop team:

PIR – Azure Virtual Desktop connection failures 
The activity log alert Service Health Alerts was triggered by a service issue for the Azure subscription Pay-As-You-Go. 
View in Azure Service Health >

 TRACKING ID: KR8C-K1Z
TYPE: Incident 
STATUS: RCA

  COMMUNICATION: 
What happened?
Between 01:00 UTC and 23:30 UTC on 29 April 2026, a platform issue resulted in an impact to the Azure Virtual Desktop service across multiple regions. Impacted customers experienced intermittent failures or difficulty establishing connections when accessing their virtual desktops using supported clients.

What went wrong, and why?
A recent hotfix deployment introduced a code regression that affected the Azure Virtual Desktop connection stack for a subset of customers. This regression caused elevated internal error rates during connection establishment, leading to intermittent connection failures. As a result, affected customers were unable to reliably connect to their virtual desktops until mitigation actions were applied.
How did we respond?
•	01:00 UTC on 29 April 2026 – Customer impact began.
•	01:30 UTC on 29 April 2026 – The issue was detected through internal service monitoring alerts, followed by customer support escalations.
•	02:30 UTC on 29 April 2026 – A recent hotfix–related regression was identified as the contributing cause.
•	23:00 UTC on 29 April 2026 – We have reverted affected customers to a previously stable service version to restore connectivity. We rolled back from AVD SxS Network Stack version 1.0.2602.09500 to the previous deployed version 1.0.2602.09400.
•	23:30 UTC on 29 April 2026 – Service was restored, and customer impact was mitigated.
What happens next?
•	This Mitigation Statement is the final communication for this incident. For details about which Azure incidents qualify for which Post Incident Reviews (PIRs), refer to https://aka.ms/AzurePIRs
•	The impact times above represent the full incident duration, so are not specific to any individual customer. Actual impact to service availability may vary between customers and resources – for guidance on implementing monitoring to understand granular impact: https://aka.ms/AzPIR/Monitoring
•	To stay informed about future Azure service issues, make sure that you configure and maintain Azure Service Health alerts – these can trigger emails, SMS, push notifications, webhooks, and more: https://aka.ms/ash-alerts
•	For broader guidance on preparing for cloud incidents, refer to https://aka.ms/incidentreadiness

IMPACTED SERVICE(S) AND REGION(S)
Service Name: Windows Virtual Desktop

Regions: 
Australia East
Australia Southeast
Canada Central
Canada East
Central India
Japan East
Japan West
North Europe
South India
UK South
UK West
West Europe

Answer 2

Mario Velazquez hi & thx for join me here at Q&A portal,

0x204 for all users at same time usually means this is not a user profile issue, its either AVD service/region issue or session hosts unavailable.

Look at Azure Service Health for Canada East / AVD incidents.

check host pool status session hosts must be running, available, not in drain mode, and agent status must be healthy. Is FSLogix/profile storage or domain/Entra auth is down because users can fail before desktop opens.

if only external users fail, check firewall/proxy blocking AVD required FQDNs. since this started today for everyone, dont waste time reinstalling client first. collect one failed connection correlation ID from Remote Desktop client and open support ticket if host pool looks healthy.

means all users + same time = service/host pool issue, check Service Health and AVD agent/session host health first

rgds, Alex

&

if my answer helps pls accept it.

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Getting error 0x204 when user try to connect to Azure virtual Desktop

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