Better: I Remote Desktop Connection Error Code 0x904

Ensure that Remote Desktop (WebSocket) is allowed through the Windows Defender Firewall on both the client and host machines. If using a VPN, ensure it is stable; switching from a computer name to a direct IP address in the connection field can also bypass local DNS resolution issues.

✅ – Request a machine certificate from your domain CA and bind it to RDP via wmic or the registry.

More precisely, it is a during the RDP handshake. The client receives a certificate from the RDP server (Windows, Azure Virtual Desktop, or third-party gateway), but the client rejects it. i remote desktop connection error code 0x904 better

On the computer:

| Layer | What fails | Why | |-------|------------|-----| | | No | TCP port 3389 or custom port is reachable. | | TLS handshake | Yes | Certificate chain cannot be verified by the client. | | CredSSP | Not reached | The error occurs before NLA (Network Level Authentication). | Ensure that Remote Desktop (WebSocket) is allowed through

If only some servers are affected, a silent certificate expiration is likely the culprit. Log into the host locally. Open (Certificates console).

Sometimes the service responsible for resolving names gets stuck. More precisely, it is a during the RDP handshake

$path = "HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services" Set-ItemProperty -Path $path -Name "SecurityLayer" -Value 0 -Type DWord

Go to the Azure Portal, select your VM, and choose .

Unlike generic connection failures, Error 0x904 usually points to underlying network instability, misconfigured firewall rules, or aggressive power-saving settings. Below is a comprehensive guide to understanding this error and fixing it permanently. Understanding the Root Causes of Error 0x904

| Error | Layer | Cause | |-------|-------|-------| | | TLS | Certificate validation failure | | 0x907 | CredSSP | Encryption oracle remediation (CVE-2018-0886) | | 0x516 | Network | TCP timeout / firewall | | 0x104 | Licensing | No RDS CAL available | | 0x80090302 | Security | Unsupported security protocol (e.g., server requires TLS 1.2, client only 1.0) |