I had the same error on ESXi, 6.0.0, 2494585
Using SSH to the VMWare server edit /etc/ntp.conf
add (according to your timezone):
server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org
In the server configuration -> Software -> Security Profile -> Services -> Properties -> Remote access
Pick NTP Daemon (for me was Stopped)
Below under Service properties click on Options:
Setup as in Time configuration
The NTP client start working.