Thanks for the reply Uli. Pasted output below

Also, I was scratching my head some more after sending the previous email. Would I run the two lines below to add these links manually? Or should I do something more/else? 
ln -s /usr/lib64/libNX_X11.so.6     /usr/lib64/nx/X11/libX11.so.6
ln -s /usr/lib64/libNX_X11.so.6.3.0 /usr/lib64/nx/X11/libX11.so.6.3.0

Best, A.

$ ldd /usr/bin/nxagent
linux-vdso.so.1 =>  (0x00007ffe21fc2000)
libtirpc.so.1 => /lib64/libtirpc.so.1 (0x00007fa9d1cd4000)
libX11.so.6 => /lib64/libX11.so.6 (0x00007fa9d1995000)
libXcomp.so.3 => /lib64/libXcomp.so.3 (0x00007fa9d166c000)
libXcompshad.so.3 => /lib64/libXcompshad.so.3 (0x00007fa9d1460000)
libXrender.so.1 => /lib64/libXrender.so.1 (0x00007fa9d1254000)
libXfixes.so.3 => /lib64/libXfixes.so.3 (0x00007fa9d104e000)
libXfont.so.1 => /lib64/libXfont.so.1 (0x00007fa9d0e1a000)
libXcomposite.so.1 => /lib64/libXcomposite.so.1 (0x00007fa9d0c16000)
libXinerama.so.1 => /lib64/libXinerama.so.1 (0x00007fa9d0a13000)
libXdmcp.so.6 => /lib64/libXdmcp.so.6 (0x00007fa9d080d000)
libNX_X11.so.6 => /lib64/libNX_X11.so.6 (0x00007fa9d04c9000)
libXext.so.6 => /lib64/libXext.so.6 (0x00007fa9d02b7000)
libz.so.1 => /lib64/libz.so.1 (0x00007fa9d00a1000)
libm.so.6 => /lib64/libm.so.6 (0x00007fa9cfd9e000)
libXpm.so.4 => /lib64/libXpm.so.4 (0x00007fa9cfb8c000)
libxml2.so.2 => /lib64/libxml2.so.2 (0x00007fa9cf822000)
libpixman-1.so.0 => /lib64/libpixman-1.so.0 (0x00007fa9cf578000)
libpng15.so.15 => /lib64/libpng15.so.15 (0x00007fa9cf34d000)
libjpeg.so.62 => /lib64/libjpeg.so.62 (0x00007fa9cf0f8000)
libc.so.6 => /lib64/libc.so.6 (0x00007fa9ced2a000)
libgssapi_krb5.so.2 => /lib64/libgssapi_krb5.so.2 (0x00007fa9ceadd000)
libkrb5.so.3 => /lib64/libkrb5.so.3 (0x00007fa9ce7f5000)
libk5crypto.so.3 => /lib64/libk5crypto.so.3 (0x00007fa9ce5c1000)
libcom_err.so.2 => /lib64/libcom_err.so.2 (0x00007fa9ce3bd000)
libnsl.so.1 => /lib64/libnsl.so.1 (0x00007fa9ce1a3000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007fa9cdf86000)
libxcb.so.1 => /lib64/libxcb.so.1 (0x00007fa9cdd5e000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007fa9cdb5a000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007fa9cd852000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fa9cd63c000)
libXdamage.so.1 => /lib64/libXdamage.so.1 (0x00007fa9cd439000)
libXrandr.so.2 => /lib64/libXrandr.so.2 (0x00007fa9cd22d000)
libXtst.so.6 => /lib64/libXtst.so.6 (0x00007fa9cd027000)
libfreetype.so.6 => /lib64/libfreetype.so.6 (0x00007fa9ccd81000)
libfontenc.so.1 => /lib64/libfontenc.so.1 (0x00007fa9ccb79000)
/lib64/ld-linux-x86-64.so.2 (0x00007fa9d25bd000)
liblzma.so.5 => /lib64/liblzma.so.5 (0x00007fa9cc953000)
libkrb5support.so.0 => /lib64/libkrb5support.so.0 (0x00007fa9cc744000)
libkeyutils.so.1 => /lib64/libkeyutils.so.1 (0x00007fa9cc540000)
libresolv.so.2 => /lib64/libresolv.so.2 (0x00007fa9cc327000)
libXau.so.6 => /lib64/libXau.so.6 (0x00007fa9cc122000)
libXi.so.6 => /lib64/libXi.so.6 (0x00007fa9cbf12000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007fa9cbcea000)
libpcre.so.1 => /lib64/libpcre.so.1 (0x00007fa9cba88000)





On Mon, Aug 20, 2018 at 1:09 PM, Ulrich Sibiller <ulrich.sibiller@gmail.com> wrote:
You seem to be missing a libX11 link to libNX_X11. Please run ldd /usr/bin/nxagent and post the result.

Uli

Alec Bayo <alec.bayo@gmail.com> schrieb am Mo., 20. Aug. 2018, 19:48:
Hi all,

Asking for help please troubleshooting an issue with x2go.

Inbound connections stopped working after I updated the kernel and nvidia drivers on my centos workstation (the x2go server).  

On the client, the error message says "Connection failed. Failed to start X2Go Agent session with ID account-_____. X2Go Agent terminated unexpectedly. Aborting session startup."

[If I attempt a connecion again the client shows a previous apparently pre-existing connection, but I cannot resume it.]

On the server, the session log says "Error: Aborting session with 'Unable to open display 'nx/nx,options=...". I have attempted uninstalling and reinstalling x2goserver from epel.

This symptoms are similar to an issue Mihai Moldovan resolved for Qianqian Fang in April: https://www.mail-archive.com/x2go-user@lists.x2go.org/msg02809.html

However, I do not have the offending line set in LD_LIBRARY_PATH which solved the issue for Qianqian.

#Contents of LD_LIBRARY_PATH (this is from env after ssh-in).
LD_LIBRARY_PATH=/usr/local/cuda/lib64:/home/[...]/caffe/distribute/lib/::/usr/lib:/usr/lib/python2.7

I also attempted commenting out this setting from .bashrc, and that did not fix it.

I've copied below answers to some questions Mihai asked Qianqian. The only strange thing I noticed is that Mihai asked for the contents of /usr/lib64/nx/X11 , and this is empty. The library Qianqian listed in there is located at /usr/lib64 on my server.

Some more details below, answering questions that were made on this earlier, similar troubleshooting request.

Best regards, thanks for any help,
Ale


# Please make sure that nx-libs 3.5.99.16 is installed on the server side:
Package nx-libs-3.5.99.16-1.el7.x86_64 already installed and latest version

# Client up to date:
x2goclient is already the newest version (4.1.1.1-2).

 # Perhaps this is useful, these lines are also from env:
QTDIR=/usr/lib64/qt-3.3
QTINC=/usr/lib64/qt-3.3/include
SSH_TTY=/dev/pts/1
QT_GRAPHICSSYSTEM_CHECKED=1
QTLIB=/usr/lib64/qt-3.3/lib
QT_PLUGIN_PATH=/usr/lib64/kde4/plugins:/usr/lib/kde4/plugins


# Contents of /usr/lib64/nx/X11  

$ ls /usr/lib64/nx
bin  X11

$ ls -lah  /usr/lib64/nx/X11
total 0
drwxr-xr-x. 2 root root  6 Aug 18 14:28 .
drwxr-xr-x. 4 root root 26 Aug 18 14:28 ..

$ ls -lah  /usr/lib64/nx/bin
total 0
drwxr-xr-x. 2 root root 36 Aug 17 21:28 .
drwxr-xr-x. 4 root root 26 Aug 18 14:28 ..
lrwxrwxrwx. 1 root root 16 Aug 17 16:09 nxagent -> /usr/bin/nxagent
lrwxrwxrwx. 1 root root  7 Aug 17 21:28 x2goagent -> nxagent

$ ls -lah  /usr/bin/nxagent
-rwxr-xr-x. 1 root root 4.5M Jul 18 17:47 /usr/bin/nxagent

# Where I found the related libraries

$ ls -lah /usr/lib64/*NX*
lrwxrwxrwx. 1 root root   18 Aug 18 14:15 /usr/lib64/libNX_X11.so.6 -> libNX_X11.so.6.3.0
-rwxr-xr-x. 1 root root 1.3M Jul 18 17:47 /usr/lib64/libNX_X11.so.6.3.0



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