After much ado and following forum advice, I finally managed to have ACX check show in the plug-ins and unfortunately after I hit ‘enable’ I had this message pop up:
Effect or command at Users/Macbook/Library/Application Support/audacity/Plug-Ins/acx-check.ny failed to register:
ill formed nyquist plug-in heade.
Any ideas! I’m desperate now! Thank in advance! 
The error message means that there’s something wrong with the file “acx-check.ny”. I’d suggest that you try downloading it again. If you still get the same problem, please attach the file to your reply so that we can see what’s wrong with it.
Acx-check.ny (9.01 KB)
See if that works any better.
ACX Check is the shortcut tool. You don’t have to do it that way. You can use the legacy tools.
http://www.kozco.com/tech/audacity/ACXTesting/ACXTesting.html
It works, but it’s pretty painful. That’s why we wrote ACX Check.
Koz