While the official Microsoft RDP protocol documentation (MS-RDPBCGR) doesn't provide a specific mapping for the 0x904 error code, community research and technical analysis indicate its most common root cause: The connection is interrupted right before or during the essential security handshake between your local client and the remote server. This often manifests as a issue. To better understand what might be causing this, let's categorize the issues and explore how to fix them.
RDP uses both TCP and UDP packets. If a router or VPN drops the UDP packets during the handshaking phase, error 0x904 occurs. Switching to TCP fixes this stability issue. Press Windows Key + R , type gpedit.msc , and press Enter .
: If you are connecting over a VPN, a "dodgy" or slow connection often triggers this specific code. Try disconnecting and reconnecting the VPN before attempting the RDP session again. Additional Troubleshooting RDP uses both TCP and UDP packets
: Antivirus suites or firewalls (such as Bitdefender) may flag the outbound or inbound RDP tunnel as a threat. How to Fix RDP Error Code 0x904 / 0x7 1. Clear and Renew Expired RDP Certificates
This error usually appears with a message saying, with the following details: Press Windows Key + R , type gpedit
In the "Computer" field, click the dropdown and delete the IP/Name of the problematic host. Open and go to C:\Users\%Username%\Documents .
: Outdated or corrupted passwords in Windows Credential Manager. In this scenario
If you're still unable to connect after working through all these steps, a more complex system conflict may be at play. In this scenario, your best course of action is to consult the detailed logs in the (Windows Logs > Application and System), which can often provide more specific clues. For further assistance, consider posting your findings (including any new error codes from the Event Viewer) on a community forum like the Microsoft Q&A for personalized support.