Can't connect using RDP over TLS without NLA

Hi,

I have special circumstances where I need to connect (RDP using MSTSC) to a Windows server that enforces RDP over TLS, but without NLA (enablecredsspsupport:i:0 in the RDP file, the server allow this).

On some clients (I saw this only with Windows Server 2012 R2 clients) I'm getting the following error: "The connection cannot proceed because authentication is not enabled . . .".

The only thing I found online was to change the authentication level, which didn't help.

I analyzed the traffic using Wireshark and I believe the problem is with the RDP negotiation, where the client sends a list of it's supported security protocols. If I connect from the same client with NLA (enablecredsspsupport:i:1) I get this:

requestedProtocols:
    .... .... .... .... .... .... .... ...1 = TLS security supported: True
    .... .... .... .... .... .... .... ..1. = CredSSP supported: True
    .... .... .... .... .... .... .... 1... = Early User Authorization Result PDU supported: True

But if I connect with enablecredsspsupport:i:0 I get this:

requestedProtocols:
    .... .... .... .... .... .... .... ...0 = TLS security supported: False
    .... .... .... .... .... .... .... ..0. = CredSSP supported: False
    .... .... .... .... .... .... .... 0... = Early User Authorization Result PDU supported: False

Where I would expect this (I do get this with some clients):

requestedProtocols:
    .... .... .... .... .... .... .... ...1 = TLS security supported: True
    .... .... .... .... .... .... .... ..0. = CredSSP supported: False
    .... .... .... .... .... .... .... 0... = Early User Authorization Result PDU supported: False

It seems like for some reason disabling CredSSP on the client also disables TLS.

I would appreciate if someone could help me figure out what's happening.

Thanks,
Gabriel