diff --git a/Apache-Guacamole-managed-by-EGroupware.md b/Apache-Guacamole-managed-by-EGroupware.md
index 14c2136..d700e4e 100644
--- a/Apache-Guacamole-managed-by-EGroupware.md
+++ b/Apache-Guacamole-managed-by-EGroupware.md
@@ -2,6 +2,8 @@ Guacamole makes RDP or VNC desktops available via html5 inside EGroupware.
 EGroupware supplies account information, authentication via OpenID Connect
 and allows to manage connections.
 
+![GuacamoleWindows2016Server](https://user-images.githubusercontent.com/972180/79756536-0df90280-831b-11ea-97ff-b3043d7b31e4.png)
+
 ### EGroupware Guacamole app does the following:
 
 * Installs all tables (or views) for Apache Guacamole
@@ -38,6 +40,16 @@ HTTP_HOST=example.org apt install egroupware-guacamole
 
 ### Troubleshooting
 
+* Guacamole can't connect to windows machine:
+
+![NLA-error](https://user-images.githubusercontent.com/972180/79778713-7bb42700-8339-11ea-9dd9-eda38ee40966.png) ![NLA-error-german](https://user-images.githubusercontent.com/972180/79778716-7c4cbd80-8339-11ea-9bed-29d2808b3ec3.png)
+
+> Remote Desktop Protocol need to be enabled AND Network Level Authentication need to be disabled (or username and password specified in the connection)
+
+![NLA-Dialog](https://user-images.githubusercontent.com/972180/79756542-0f2a2f80-831b-11ea-801b-4acf9577db2e.png) ![NLA-Dialog-German](https://user-images.githubusercontent.com/972180/79756540-0e919900-831b-11ea-9732-0277ebbfc8f3.png)
+
+Network Level Authentication is a security measure mitigating risks of RPD exposed to the Internet, which is not the case for Guacamole used to make desktops available via HTML5, using strong authentication mechanisms available in EGroupware like TwoFactorAuth or WebAuthn.
+
 * check the log of the guacamole container (almost all of the problem below are reported there!)
 ```
 docker logs -f guacamole