Package:X2Go Server
Version : 4.0.1.20
System : Ubuntu 17.04 Zesty Zapatus, Kernel 4.4.0-81-generic
Desktop: MATE 1.18.0

After Launching the Client, it shows a black Window, showing "Could not acquire name on session bus"

First I suggested to edit the file /etc/systemd/system/display-manager.service - but  that is wrong, 
then the desktop on the machine will note come up : 

***** WRONG : /etc/systemd/system/display-manager.service

[Service]
unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS
.....

***** /WRONG - Desktop Session will not boot this way (remote desktop is working)

***** /etc/x2go/Xsession.d/75dbus_dbus-launch

# $Id:$
# In order to activate the session bus at X session launch
# simply place use-session-dbus into your /etc/X11/Xsession.options file
#

STARTDBUS=
DBUSLAUNCH=/usr/bin/dbus-launch
if has_option use-session-dbus; then
  # changed rn am 26.06.2017 - $DBUS_SESSION_BUS_ADDRESS is not zero length, but : "unix:path=/run/user/1000/bus"
  # if [ -z "$DBUS_SESSION_BUS_ADDRESS" ] && [ -x "$DBUSLAUNCH" ]; then  # old code - STARTDBUS will ne not set
  if [ -x "$DBUSLAUNCH" ]; then						 # new code - STARTDBUS will be set to yes
    STARTDBUS=yes
  fi
fi

if [ -n "$STARTDBUS" ]; then
  # Note that anything that is D-Bus-activated between here and
  # 95dbus_update-activation-env will not have the complete environment
  # set up by Xsession.d, unless the Xsession.d snippet that sets the
  # environment variable also calls dbus-update-activation-environment.
  # See <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815503>
  eval $($DBUSLAUNCH --exit-with-session --sh-syntax)
fi

***** /etc/x2go/Xsession.d/75dbus_dbus-launch - now its working as expected on my machine ... 

yours sincerely

Ing. Robert Nowotny
Rotek GmbH