I've written an ExternalParameter in my nxagentd.conf file that looks like this:

ExternalParameter = NTP.Check(*):/usr/sbin/ntpdate -q -p1 $1 | /bin/grep "0.00000" | /usr/bin/wc -l

Running this command on the host works fine. However, when I query it from the server I receive the error:

Cannot get current parameter value: Communication failure

I have several other ExternalParameters on this agent, all working correctly. Any insight into this?