RDP login error Windows 10 to Windows 7 (LSA error on client, Event 56 on host)

Question

I've spent the last hour or so trying to solve an RDP issue between Windows 10 (we've tried several machines that are regularly used for RDP) and a remote Windows 7 machine. This connection has been used often for several years.

Over the past few weeks we have been unable to get an RDP connection, with the following symptoms.

Client (Windows 10)

The Local Security Authority cannot be contacted
This could be due to an expires password.

Server (Windows 7 - Event Log)

TermDD Code 56: The Terminal Server security layer detected an error in the protocol stream

I've checked the obvious possible issue mentioned in the client error but the password has not expired.

I've researched code 56 but nearly everything online relates to more random freezing / disconnects, with network issues being blamed primarily. I am getting the error instantly on login, and have a rock solid TeamViewer connection whilst trying to solve this so it doesn't seem to be the same issue.

I've also tried installing the RDP 8 update on the client in the hopes it might reset something in the RDP server and fix it, but I'm still getting exactly the same problem

Has anyone else seen this issue or know of a possible solution?

Answer 1

This isn't really the "right" solution but it seems changing the remote settings to Allow connections from computers running any version of Remote Desktop allows me to connect.

Obviously I'd rather leave this set to the NLA option so it will still be useful if anyone else has some input on what might be causing this issue.

Answer 2

I was suffering the from the same issue and found a fix in KB 4487345 and it's downloadable in Microsoft's update catalog

Microsoft's patches from 2018-01-08 introduced "security fixes" in Windows 7 and 2008 R2 that broke remote access for users who are admins locally (on the server).

This was my initial source with a more detailed description.