Hi!
If it's running on another IP it's most likely not the other FreePBX which is causing you problems...
Is that new FreePBX box in a DMZ and was it configured to be very restrictive as to what the server is allowed to do?
The command give in the wiki works from the actual Linux command line (or directly from Asterisk CLI if you remove everything before the mail and replace it with "!" (exclamation mark) but at lest with FreePBX 13 it doesn't work with the Asterisk CLI provided in the web interface for me...
Good luck and have a nice day!
Nick