I have recently installed a complete x2go setup on a single server with the 
standalone http broker and am encountering the same problem. For me too it 
appears like not checking for sessions to resume in x2goclient is intentional, 
as message #80 by Oleg indicates.

Now I read on the wiki that if the broker is used the broker is responsible 
for session resumption, which makes sense to me. The x2goclient then just does 
whatever the broker tells it to.

This results in the following question, which I haven't been able to find an 
answer for: How to configure the reference broker to resume sessions 
automatically instead of always spawning a new session?

I have only a single session type configured in the inifile, and the intention 
is that when a client connects, selecting this selection the broker should 
resume an existing session of the same type if one exists. At no point should 
there be more than one sessions of the same type.

If I add the SHADOW session type to the inifile I can actually see the 
suspended sessions and interact with them properly. But even if there are 
sessions suspended, selecting the KDE session results in a new session, 
always.

Also seems that x2gobroker.conf default-session-autologin=true does not work 
for SHADOW session type, it uses my regular SSH key. This is a different issue 
though which will post elsewhere shortly.

Thanks.