The most common fix is ensuring you are not logged into the remote computer elsewhere.
When attempting to install an update, patch, or feature related to Remote Desktop Connection (mstsc.exe) or when an RDP session initialization triggers an automatic component installation, the system returns: i remote desktop connection error code 0x904 install
If you cannot change the server certificate (e.g., connecting to a legacy machine), you must tell the client to ignore the error. The most common fix is ensuring you are