Why status of VNC service showing as failed ?

Issue

• VNC server is configured. But, the status is showing as failed.

   $ systemctl status vncserver@:1.service
  ● vncserver@:1.service - Remote desktop service (VNC)
    Loaded: loaded (/etc/systemd/system/vncserver@:1.service; enabled; vendor preset:   disabled)
   Active: failed (Result: exit-code) since Wed 2018-08-01 10:50:07 +04; 12s ago
   Process: 14759 ExecStart=/usr/sbin/runuser -l vncuser -c /usr/bin/vncserver %i        (code=exited, status=1/FAILURE)
   Process: 14756 ExecStartPre=/bin/sh -c /usr/bin/vncserver -kill %i > /dev/null 2>&1        || : (code=exited, status=0/SUCCESS)
   Main PID: 3456 (code=exited, status=0/SUCCESS)