Blocker Description
Hello,
I'm trying to establish an RDP connection on a Windows 2012 R2 server but I can't!
Here is what is displayed in the logs
/var/log/syslog
Jun 17 10:58:17 monserv guacd[2900]: Creating new client for protocol "rdp
Jun 17 10:58:17 monserv guacd[2900]: Connection ID is "$f2c802be-d3e6-4c4d-b728-16a25f434afc"
Jun 17 10:58:17 monserv guacd[29127]: Security mode: Negotiate (ANY)
Jun 17 10:58:17 monserv guacd[29127]: Resize method: none
Jun 17 10:58:17 monserv guacd[29127]: User "@e358a6d7-d058-49ec-a467-7b33103ee346" joined connection "$f2c802be-d3e6-4c4d-b728-16a25f434afc" (1 users now present)
Jun 17 10:58:17 monserv guacd[29127]: Loading keymap "base"
Jun 17 10:58:17 monserv guacd[29127]: Loading keymap "en-ch-qwertz"
Jun 17 10:58:17 monserv guacd[29127]: Connected to RDPDR 1.12 as client 0x0004
Jun 17 10:58:17 monserv guacd[2900]: Connection "$f2c802be-d3e6-4c4d-b728-16a25f434afc" removed.
/var/log/tomcat8/*
==> localhost_access_log.2021-06-17.txt <==
172.17.17.21 - - [17/Jun/2021:11:07:46 +0000] "POST /guacamole/api/tokens HTTP/1.1" 200 183
==> catalina.out <==
11:07:56.645 [http-nio-172.17.17.21-8081-exec-5] INFO o.a.g.tunnel.TunnelRequestService - User "monadmin" connected to connection "2".
11:07:57.126 [Thread-44374] INFO o.a.g.tunnel.TunnelRequestService - User "monadmin" disconnected from connection "2". Duration: 480 milliseconds
No obvious errors in the logs 
In the interface, I have a black screen and the connection is immediately opened !
I had tried (without restarting the server because it is currently in production) to disable in the RDP settings of the server the option "NLA authentication" but it does not change anything
My Guacamole server is installed on a Debian 9.13. I installed directly from the tar.gz retrieved from Sourceforge.net (https://sourceforge.net/projects/guacamole/files/current/source/guacamole-client-0.9.14.tar.gz/download)
Many thanks