Having some trouble on 3.5.1

This seems like a really good addition to our plugins, but I can’t seem to make it work within Nagios. Reports metrics as expected from the command line, from any directory and as the nagios user, but I can only get a “null” response within nagios. I can’t figure out what I’m missing.
I even tried the “–help” option as an argument and still only get a “null” return status.
Anybody else had a similar experience?

thanks