Gnome can not auto login

[wenzi]

I use gnome with gdm,but now I can not auto login. when I start the system it will get the desktop ,but for 3 second ,it will back to the login interface .
here is /etc/gdm/custom.conf:
cat /etc/gdm/custom.conf
# GDM configuration storage

[daemon]
# Uncomment the line below to force the login screen to use Xorg
#WaylandEnable=false

AutomaticLoginEnable=True
AutomaticLogin=XXX

[security]

[xdmcp]

[chooser]

[debug]
# Uncomment the line below to turn on debugging
#Enable=true

[wenzi]

maybe it's wrong of the gdm ,I change to lightdm ,it's became well