GLX not working on Fedora 25 w/ nvidia driver
 

[jks@jks-desktop ~]{f25}$ glxinfo
name of display: :0
Error: couldn't find RGB GLX visual or fbconfig

[jks@jks-desktop ~]{f25}$ glxgears
Error: couldn't get an RGB, Double-buffered visual

[jks@jks-desktop ~]{f25}$ uname -a
Linux jks-desktop 4.11.4-200.fc25.x86_64 #1 SMP Wed Jun 7 18:28:00 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

[jks@jks-desktop ~]{f25}$ egrep -i glx /tmp/Xorg.0.log
[ 53.101] (II) LoadModule: "glx"
[ 53.103] (II) Loading /usr/lib64/nvidia/xorg/libglx.so
[ 53.182] (II) Module glx: vendor="NVIDIA Corporation"
[ 53.183] (II) NVIDIA GLX Module 375.66 Mon May 1 14:28:39 PDT 2017
[ 54.122] (II) Initializing extension GLX
[ 54.122] (II) Indirect GLX disabled.

[jks@jks-desktop ~]{f25}$ lsmod | egrep "(nvidia|nou)"
nvidia_drm 49152 1
nvidia_modeset 790528 3 nvidia_drm
nvidia 12308480 41 nvidia_modeset
drm_kms_helper 151552 1 nvidia_drm
drm 348160 4 nvidia_drm,drm_kms_helper

Any ideas? GLX works on the same machine with Fedora 20.

Hasn't Fedora just moved to Wayland, which NVIDIA don't [yet?] support?
You may just need to choose an non-Wayland desktop.

I thought only when using Gnome. I'm using xfce.

True, XFCE's not yet gone Wayland.